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PDA Glossary

PDA Glossary of Pharmaceutical and Biotechnology Terminology

PDA Technical Reports are highly valued membership benefits because they offer expert guidance and opinions on important scientific and regulatory topics and are used as essential references by industry and regulatory authorities around the world. These reports include terms which explain the material and enhance the reader’s understanding.

The database presented here includes the glossary terms from all current technical reports. The database is searchable by keyword, topic, or by technical report. Each definition provided includes a link to the source technical report within the PDA Technical Report Portal.

Browse Terms by Title


Browse Terms by TR #

  • Tailgate Sample

    Representative and random samples of the lot taken by the manufacturer during the packing process for the use of incoming inspection purposes. (TR76)

  • Tailing

    Deviation from first-order death kinetics in a microbial population observed when the logarithm of the number of survivors is plotted against time. The “tail” of the survivor curve represents organisms surviving for times in excess of those that would be predicted from first-order kinetics. (TR51)

  • Taints

    Taints are unpleasant odors and tastes due to low levels of organic compounds of natural or human-derived origin in food, beverages and drug products. Taints arise from an external source as opposed to off-odors or off-flavors from internal changes to a product (i.e., microbial spoilage). (TR55)

  • Tangential Flow Filtration

    Filtration in which the product stream is introduced parallel to the membrane surface and flows in a direction perpendicular to the filtrate flow. (Synonym:cross-flow filtration) (TR15)

  • Tangential or Cross Flow Filtration (TFF or CFF)

    Filtration in which a fluid (feed) stream runs tangential to a membrane. A pressure differential causes some fluid to pass through the membrane. (TR41)

  • Target Criteria

    Numerical limits, ranges, or other suitable measures of target performance levels of an analytical method that indicate suitable performance for intended use. For a method entering qualification, this is a target performance criterion that, when assessed, indicates that the method is qualified for its intended purpose. (TR57-2)

  • Target Product Profile (TPP)

    A format for a summary of a drug development program described in terms of labeling concepts to facilitate communication regarding a particular drug development program. (TR60) (TR60-2)

  • Targeted Species

    The range of species for which detection or analysis is aimed for by an assay method. (TR50)

  • TCld50 Assay

    Quantal assays for determining the titer of a virus. The 50% tissue culture infective does (TCID50) is the dilution of virus that results in the infection of 50% of cell cultures that have been infected with the same dilution of the virus sample. (TR47)

  • Technical Diligence

    The means by which the technical capabilities of the SUS, its supplier and its fit with the end user are verified. It is complimentary to a quality audit program and becomes a recurring theme over the implementation process and subsequent routine procurement. (TR66)

  • Technically Unavoidable Particles (TUPs)

    Particles that are visibly different from the bulk of the material when viewed with the naked eye within the container or against a suitable back­ground (e.g., size, shape, color, number, texture) and are inherent to the manufacturer’s process, product, or raw materials. The unintended pres­ence of a small quantity of particles, stemming from impurities of natural or synthetic ingre­dients, the manufacturing process, storage, or migration from packaging that is technically un­avoidable in good manufacturing practice, and do not pose a risk to patient safety. (TR78)

  • Temperature

    Temperature is the measure of thermal energy. (TR01)

  • Temperature Control Unit (TCU)

    A unit that controls the refrigeration and heating systems. It typically contains a microprocessor and thermostat to maintain the set temperature. (TR64)

  • Temperature Controlled

    The sequence of transportation events, from the manufacturer of the API up to the receipt of the final packaged product by the end user, which maintains temperature sensitive products within approved temperature specifications. Maintaining temperature control during these transportation events assures that product quality is maintained. (TR39)

  • Temperature Distribution

    Temperature measurement of the heating medium (e.g., forced hot air) across the chamber load zone. (TR01) (TR03) (TR30) (TR48)

  • Temperature Excursion

    Any event in which product is exposed to temperatures outside of the recommended storage and/or transport temperature range. (TR39)(TR58)

  • Temperature Monitor

    A unit that measures the prevailing temperature. Several types exist, including:
    • Stationary monitors installed in (cold) storage warehouses or storage facilities;
    • Mobile monitors that include:
    • Chemical indicators that change color when exposed to temperature over time
    • Electronic indicators that indicate temperature excursions, but provide little or no summary data
    • Electronic or mechanical data loggers that record and store temperature data for retrieval after arrival
    • Transmitting monitors that transmit near real-time data and excursion events using wireless/satellite interfaces and software for “logical analysis” of data. (TR58)

  • Temperature Probe

    A sensor (e.g., thermocouple or resistance temperature detector (RTD)) that has been specifically designed to measure temperature. Temperature probes may be control, resident, surface mounted, validation, mapping, or permanent. (TR61)

  • Temperature Probe/Sensor

    A generic term used to describe any type of temperature measuring device that works through contact with the material or atmosphere to be measured. [Synonyms: Load Probe, Heat Penetration Probe, Temperature Distribution Probe, Drain Probe] (TR48)

  • Temperature Profile

    Anticipated ambient temperature variation and duration to which product may be exposed during transportation. (TR39)

  • Temperature Sensitive Products

    Products whose quality may be adversely affected by temperature extremes (e.g., frozen, refrigerated, and certain controlled room temperature products). (TR39)

  • Temperature-Controlled Distribution

    Material handling and movement of goods from an origin site to a receiving site, where the goods are kept within a specified temperature range using active and/or passive systems. (TR58)

  • Temperature-Controlled Ocean Container

    An actively cooled metal box, most commonly 20 or 40 foot long which can be easily transferred between different modes of transportation, such as ships, trains and trucks. Sometimes it is called a reefer container or intermodal container. (TR58)

  • Temperature-Controlled Ocean Container (Reefer, Intermodal Container)

    An actively cooled metal box (commonly 20 or 40 ft long) that can be easily transferred between different modes of transportation, such as between ships, trains, and trucks. (TR64)

  • Temperature-Controlled Truck or Trailer

    A cargo box attached to a truck chasse or as a trailer pulled by a truck that is equipped with a temperature control unit (TCU) to provide active cooling or heating control inside the box. Refrigerated trucks or trailers are sometimes referred to as “reefers”. The temperature control units are typically powered by an integrated engine or gen-set and not the engine that is used to propel the truck. (TR58)

    A cargo box attached to a truck chassis or consisting of a trailer pulled by a truck that is equipped with a TCU to provide active cooling or heating control inside the box (refrigerated trucks or trailers are sometimes referred to as “reefers”). (TR64)

  • Terminal Sterilization

    A process whereby product is sterilized within its sterile barrier system. (TR01

    The application of a lethal agent to sealed, finished drug products for the purpose of achieving a predetermined sterility assurance level (SAL) of usually less than 10-6 (i.e., a probability of a nonsterile unit of less than one in a million). A process where the material is sterilized in its final packaged configuration. (TR13)

  • Tertiary Packaging Component

    A component that is used to assemble secondary or primary packages in the form of the basic transportation unit and to provide protection against mechanical impact. Examples are corrugated cardboard boxes, but corresponding plastic boxes/containers are also used. (TR39)

  • Test Article

    Any food additive, color additive, drug, biologi­cally derived product, etc., for human use or any other article subject to regulation. “Test Article,” in this report’s context, referring to the samples used for toxicity and stability studies. (TR56)

  • Test Sets

    A group of defect standards combined with good or blank units used to evaluate the probability of detection in visual inspection or testing system performance. Test sets can be used for inspec­tor training, validation of automated systems, or other special studies as needed. (TR79)

  • The Last Mile

    This is a multidimensional cross-industry term that defines a point in the supply chain where the product or service directly faces the customer, end user or patient. (TR46)

  • Thermal Mass

    The mass of material present multiplied by that material’s specific heat capacity. (TR64)

  • Thermocouple

    A device for measuring temperature in which a pair of wires of different metals are joined and the free ends of the wires are connected to an instrument (such as a voltmeter) that measures the electrical potential difference created at the junction of the two metals. (TR3)

  • Thermocycling

    Repetition of the PCR reaction steps of denaturing, annealing, and extension. Each step is characterized by different temperatures and reaction times. Some PCR methods combine the annealing and extension steps (i.e., two step PCR). (TR50)

  • Thermometric Study

    The utilization of independent temperature monitoring devices to determine a temperature profile within the load zone and analysis of the collected data. (TR3)

  • Throughput

    The amount of solution that passes through a filter, described as volume per membrane area. [Synonym: capacity.] (TR15)

    The amount of solution that passes through a filter. It is described as volume through the membrane area. [Synonym: capacity] (TR26)

  • Thumb Pad

    Disk at end of plunger rod. (TR73)

  • Tissue Culture Infectious Dose – TCID50

    The dilution of virus that results in the probability of infection of 50% in replicate tissue-culture inoculations. (TR41)

  • Titer

    The concentration of infectious virus calculated, taking into account the dilution factor. (TR41)

  • Titer Reduction (TR)

    A measure of the degree to which a particular filter removes a microorganism under specified test conditions. Calculated as the ratio of the total number of microorganisms used to challenge the filter divided by the total number of microorganisms that passed through the filter. (TR75)

  • Toll-like Receptor (TLR)

    A class of single membrane-spanning non-catalytic receptors that recognize structurally conserved molecules derived from microbes. They can activate immune cell responses when microbes have breached physical barriers such as the skin or intestinal tract mucosa. (TR50)

  • Total Impurities

    The sum of all impurities observed. (TR38)

  • Total Organic Carbon (TOC)

    An indirect measure of organic molecules present in pharmaceutical waters measured as carbon. (TR45)

    Measurement term for the total organic carbon in a sample. (TR70)

  • Touchdown PCR

    A technique to reduce appearance of non-specific amplicons in PCR reactions. The earliest cycles of a touchdown PCR method have high annealing temperatures. The annealing temperature is decreased in increments for subsequent cycles until a fixed point is reached. (TR50)

  • Toxicity

    The capacity of a substance to confer morbidity or mortality. In the context of virus assays, the ability of a buffer or other process components to kill or otherwise harm the functionality of indicator cell lines. This is independent of the infection by the virus. (TR41)

  • Toxicity Studies (also referred to as “Tox” studies)

    In vivo or in vitro experiments in which test ar­ticles are studied prospectively in test systems un­der laboratory conditions with the primary goals of identifying the following: 1) an initial safe dose and subsequent dose es­calation schemes in humans; 2) potential target organs for toxicity and for the study of whether such toxicity is reversible; and, 3) safety param­eters for clinical monitoring after the appropriate dosing and administering schedule is followed (relevant to the drug being studied). In toxicity studies, the test animals are examined by histo­logical or serological methods in order to iden­tify toxic, mutagenic, or teratogenic effects of the drug. It is sometimes possible to collect physi­ological data from the animals prior to sacrifice. Some toxicity studies may be performed using cell culture methods. Toxicity studies are also de­scribed by the U.S. FDA as “nonclinical labora­tory studies” and by ICH as “preclinical safety evaluations”. 

    The definition does not include studies using human subjects or clinical studies, field trials in animals, or any basic exploratory studies car­ried out to determine whether a test article has any potential utility or to determine physical or chemical characteristics as described in ICH S6 and 21 CFR Part 58 (GLP). (TR56)


  • Transcription-Mediated Amplification (TMA)

    An isothermal NAT method that can amplify RNA or DNA targets a billion-fold in less than one hour. TMA technology uses two primers and two enzymes: RNA polymerase and reverse transcriptase. (TR50)

  • Transfectoma

    Cells expressing exogenous proteins or reporter genes, produced by the transfection of continuously growing cells with gene expression constructs. (TR50)

  • Transfer Disinfection

    A disinfection process conducted on materials and equipment that coats the surface for a validated wetted time to remove bioburden prior to introducing such items into classified areas. (TR70)

  • Transition Analysis

    Mathematical evaluation of the chromatogram tracing as the mobile phase changes from one solution to another. An alternative to HETP and peak asymmetry for evaluating column packing and performance. (TR14)

  • Transmembrane Pressure (TMP)

    The pressure difference equal to the average feed-stream pressure minus the average filtrate-stream pressure. TMP = (Pfeed + Pretentate)/2 - Pfiltrate (TR15)

  • Transmission Electron Microscopy (TEM)

    A microscopy technique whereby a beam of electrons is transmitted through an ultra-thin specimen, interacting with the specimen as it passes through it. An image is formed from the electrons transmitted through the specimen, which are magnified and focused by an objective lens, and appear on an imaging screen. (TR41)

  • Transport Service Agreement

    A contractual agreement that describes the legal, logistical, technical and quality terms or contractual arrangements between shippers and transport services providers. Different names might be used for this type of agreement in different companies. (TR39)

  • Transport Service Provider

    Contracting party who mediates or executes the transportation of medicinal products on behalf of the shipper. (TR39)

  • Transportation Service Providers (TSP)

    Companies that physically transport the product. (TR52)

  • Transportation Study

    Study performed to generate data to evaluate the effect of temperature variation on the product during transportation on product quality. Other test, such as vibration, pressure, and drop tests, may be considered. (TR39)

  • Trend

    A statistical term referring to the direction or rate of change of a variable(s) (ICH Q9). (TR54) (TR54-2)

  • Trend Analysis

    Analysis of environmental data over time indicating a shift; adverse trends require investigation. (TR70)

    A review performed in response to an alert or action condition. This review provides an analysis of specific environmental monitoring data to identify adverse trends.(TR13)

  • True Copy (FDA)

    21 CFR 211.180(d) requires records to be retained "either as original records or true copies such as photocopies, microfilm, microfiche, or other accurate reproductions of the original records". Electronic copies can be used as true copies of paper or electronic records, provided the copies preserve the content and meaning of the original or raw data, which includes associated metadata and the static or dynamic nature of the original records.(TR80)(TR84)

  • True Copy (MHRA)

    A copy (irrespective of the type of media used) of the original record that has been verified (i.e., by a dated signature or by generation through a validated process) to have the same information, including data that describe the context, content, and structure as the original.(TR80)(TR84)

  • True Copy (WHO)

    A true copy is a copy of an original recording of data that has been verified and certified to confirm it is an exact and complete copy that preserves the entire content and meaning of the original record including, in the case of electronic data, all essential metadata and the original record format as appropriate.(TR80)(TR84)

  • Tub

    Plastic box that contains a vertically oriented syringe nest and is sealed with a lid. (TR73)

  • Turbidity

    Finely dispersed particles causing cloudiness or haziness in water or other fluid. Turbidity may be measured using a nephelometer. (TR45)

  • Turbulent Flow

    Movement of a fluid in which its velocity at any point varies in a random or erratic (nonlaminar) manner. (TR69)

  • Two One-Sided T-Test

    A method for declaring the comparability of equivalence that is built around comparing two or more group means and their respective mean difference confidence intervals against predetermined equivalence limits. (TR57-2)

  • Tyndall Lighting

    Collimated lighting at right angle to the viewing direction, typically against a black or dark back­ground, which is useful during manual visual inspection to detect fine dispersions of small par­ticulate that scatter the light making them more detectable. (TR79)