A glossary of culture terms

A glossary of culture terms is a decision tool. The words on a flask, a protocol and a purchase note are supposed to name different facts, and several pairs in everyday speech do not. If you swap them, you passage too late, seed the wrong number, wash cells in a solution that does not feed them, or buy a dish that will not hold an adherent line. The orientation for the whole workflow sits in mammalian cell culture for research labs. This page compares the pairs people mix.

Neighbours, not synonyms

Each pair below shares a scene. Both words can be true of one flask on one afternoon, and they still answer different questions. Confluence asks how much of a growth surface looks covered. Density asks how many cells occupy a measured area or volume. Passage asks how many times the population was subcultured. A generation, when a laboratory uses the word carefully, is closer to a doubling than to a transfer. Split ratio asks how you divided the harvest. Seeding density asks what concentration you placed in the new vessel. Viability asks which cells met a live-dead rule. Vitality, where the word is used precisely, asks about function or metabolism, not only an intact membrane.

Sterile is a claim about an object after a process. Aseptic is a claim about a handling method. Medium is a nutrient formulation. A buffer resists pH change and may contain no usable food. Primary describes cells recently explanted, with a finite culture life. Immortalised describes a population that has bypassed the usual senescence block. Adherent cells use a surface. Suspension cells grow in the liquid. Confluent describes cover. Differentiated describes a specialised phenotype. Public sheets such as the ATCC culture guides and the European Collection of Cell Cultures already separate these words. The notebook should too.

The wrong decision each mix-up causes

Confluence versus density ruins a dose. Two monolayers can both look about 70 percent covered and still differ in cells per square centimetre when one line spreads and the other stays compact. A drug added as a fixed amount per well then changes the dose per cell. The wrong decision is to copy a confluence percentage into a seeding calculation. Estimate cover when the protocol is written in cover. Count, and divide by the area the manufacturer prints, when the protocol is written in density.

Passage versus generation changes how old you think the cells are. One passage can hide one doubling or several, because a wide split forces more divisions before the flask is full again. Finite lines feel that load while the passage number still looks modest. The wrong decision is to keep a culture because it is only passage eight after aggressive splits, or to discard one as senescent when every 1-to-2 tidy-up incremented the counter. Write the supplier starting passage, your increment rule, and the split.

Split ratio versus seeding density fails when the vessel changes. One to four from a small flask into a large one is not the same surface density as the same words between equal flasks. Clumps turn a ratio into a guess. The wrong decision is to scale an experiment by flask nickname. Record cells per square centimetre or per millilitre, and if the count failed, say so.

Viability versus vitality fails at thaw and at transfection. Dye exclusion can be high while those cells still refuse to attach by morning. Membrane integrity is not metabolic reserve, and neither figure is confluence. The wrong decision is to seed an assay on one haemocytometer percent and call the population healthy. Name the dye or the metabolic readout, and say whether unattached cells were counted.

Sterile versus aseptic fails in two directions. Careful handling does not clean a contaminated culture, and a sterile bottle is not a closed system once it is open in a crowded room. Technique lowers the chance of introduction. It does not rescue a cloudy flask or bless a cap left face-down. A sterilisation cycle has a defined load and a defined claim, which is a different sentence from a claim of care, as autoclaves and what sterilisation does not do sets out.

Medium versus buffer fails in the wash. Phosphate-buffered saline and similar salts hold osmolarity and pH for a short window. They do not replace amino acids, glucose or serum. Cells parked in wash buffer during a cabinet queue are starved, and they may drift in pH if the buffer is not matched to air or to carbon dioxide. The wrong decision is to top a flask up with leftover buffer because the colour looks pale. Preparing that buffer is a separate craft in preparing a buffer and checking pH.

Primary versus immortalised fails when a continuous-line schedule is copied onto cells that still senesce. Primary cultures are often mixed, slower, and more dependent on density and on the serum or supplement lot. An immortalised population can usually be expanded further, and it can still drift. Immortalised is not a synonym for tumour-derived. The wrong decision is to skip authentication because a line grows easily, or to expect an immortal rate from a primary culture. The ICLAC register exists because names travel further than identities.

Adherent versus suspension fails at the plastic and at the count. Adherent cells need a surface made for attachment and a dissociation step that ends in single cells without shredded membranes. Suspension cells scored only on the flask floor are underestimated, because they occupy the volume. The wrong decision is to buy untreated bacterial dishes for a line that must adhere, or to discard the supernatant of a suspension culture because a copied protocol mentioned trypsin.

Confluent versus differentiated fails the day before an assay. A full monolayer can be undifferentiated, contact-inhibited, stressed, or starting a differentiation programme, depending on the line. Some protocols use cover only as a cue before a stimulus. The stimulus, the markers and the time are the differentiation. The wrong decision is to report differentiation because the plastic disappeared, or to delay a protocol that says to start before full cover.

Classes of tool that make a word true

A phase-contrast microscope supports a confluence estimate. A counter and a stated dye support density and a viability percentage. Printed growth area turns a total count into a surface density. A carbon dioxide incubator belongs with bicarbonate medium. A cabinet and a local risk assessment support aseptic work. A manufacturer's document supports a sterility claim. A short tandem repeat profile is a common identity check for a human line. Other species need the method your quality system names. None of these tools authorises a therapeutic claim.

A comparison you can put on a training sheet

Use the table as the spine of a local glossary. If a sentence in a protocol could swap the two words and still look grammatical, the sentence is not finished.

Where the workflow branches

Start from the sentence you are about to write. If you looked and did not count, record estimated confluence and do not invent a density. If you counted, record the total, the volume, the printed vessel area, and the dye. If the vial shows only a passage, do not convert it into generations. If the cells came from tissue and have not been immortalised by a stated method, call them primary.

Branch when the word's control fails. A confluence call two people cannot repeat is not a number yet. Count, or take more fields and say they disagreed. A viability percent with clumps is partly a count of clumps. A workflow that starts with a bottle still wet from a bath has already left aseptic practice. A top-up that is actually buffer is not a feed. Replace it with the formulation on the line card.

Failure modes that start as vocabulary

Speech is the usual failure. "Split them when they are full" becomes a Friday habit, and full might mean confluent or merely the flask wanted on Monday. A purchase built from one adjective fails next. Sterile plates can be untreated bacterial dishes. Adherent cells on that surface are a surface experiment. Identity language fails in the legend: calling every continuous culture primary hides the model, and calling a donor culture a stable line hides senescence. Morphology will not correct the noun.

Research use, and containment as a local decision

These definitions support research records and research purchasing. They do not diagnose a person, grade a biopsy or clear a culture for therapeutic manufacturing. Whether a given line, primary isolate or genetic modification is handled at a particular containment level is decided by the institution that holds it. A glossary cannot make that decision. Waste, disinfection and the cabinet class follow the same local assessment. Read a public culture guide as a technical starting sheet, then follow the sheet your laboratory authorised for that vial.

Heat, peeled labels and a shared sentence

In a hot, humid building, ink lifts and condensation blurs a passage number. The oral substitute, the full one or the old ones, collapses confluence, passage and vessel identity into a gesture at a shelf. Write line, passage, and either estimated cover or density before the flask goes back. A medium bottle that warmed on a receiving bench is not an unopened cold-chain lot. Keep it off a precious line until you know the supplier's stability statement. In an enquiry, state adherent or suspension, basal medium or a named buffer, treated or untreated surface, and growth area. The laboratory consumables catalogue is a map of everyday classes, not a promise about a named bottle. The academic research reference is a separate page for how a university laboratory might frame the wider work. A specification can be discussed through the quote request. EVRINTH does not run your culture suite, and a conversation about terms is not a delivery commitment.