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parameter

See characteristic, parameter, variable

pathogen, pathology

pathogen: the causative agent of a communicable disease. For example, influenza (disease) is caused by influenza virus (pathogen); malaria (disease) is caused by species of Plasmodium (pathogen). It is a common mistake to use the term for the disease when you actually mean the pathogen, and vice versa:

He contracted measles     not     He contracted measles virus
The sample was tested for measles virus     not     The sample was tested for measles

pathology: the study of diseases; do not use to mean disease

Influenza is a disease     not     Influenza is a pathology
pathology

See pathogen, pathology

patient

See consumer, patient

per cent, percentage

per cent: a term meaning units per 100

10 per cent or 10%

percentage: a statement of a quantity or rate expressed as the unit per cent

The results were expressed as percentages.

See also Relative quantities

percentage

See per cent, percentage

perform

See carry out, perform

period

See interval, period

phenotype

See genotype, phenotype

plant variety

See cultivar, hybrid, variety, plant variety

pollution

See contamination, pollution

postmortem

See autopsy, necropsy, postmortem

precision

See accuracy, precision

prediction

See forecast, prediction, projection

prevalence

See incidence, prevalence

principal, principle

principal (adjective): most important

principal (noun): a chief or head of a group (e.g. school principal)

principle (noun): a rule of conduct or a fundamental truth

See also hypothesis, law, theory

principle

See principal, principle

projection

See forecast, prediction, projection

proof

Proof is a dangerous word in the context of science because its common, scientific, mathematical and legal meanings are all different. This has been used to discredit scientists when they are asked, for example, to ‘prove’ evolutionary theory, that genetically modified foods can do no harm or that something else is irrefutably true. Such demands are at odds with the nature and process of science, which can disprove things that are untrue but be unable (philosophically) to prove them. Science is said to support propositions with varying degrees of probability (see significant, statistically significant), which may be so consistently high that the propositions can be relied on. Safer alternatives to proof that are often used include supported, established and demonstrated:

Scientists have demonstrated that Ebola is hard to contract.
Theories of global warming are well established in science.
Clinical trials have strongly supported the effectiveness of quinine.

Despite the above, proof and prove have technical meanings within science and technology – for example, ‘proving’ cannons to show that they are functional and the ‘proof’ of spirits of a certain strength.

proof (mathematics): a statement shown to be valid by logical argument

proof (legal): that which has been declared to be so by a jury, judge or legal authority