What is "onomasiology"

n. A branch of lexicology concerned with the names of concepts.

Onomasiology (from (onomāzο) — to name, which in turn is from ὄνομα — name) is a branch of linguistics concerned with the question "how do you express X?" It is in fact most commonly understood as a branch of lexicology, the study of words (although some apply the term also to grammar and conversation).

Onomasiology, as a part of lexicology, starts from a concept which is taken to be prior (i.e. an idea, an object, a quality, an activity etc.) and asks for its names. The opposite approach is known as semasiology: here one starts with a word and asks what it means, or what concepts the word refers to. Thus, an onomasiological question is, e.g., "what are the names for long, narrow pieces of potato that have been deep-fried?" (answers: french fries in the US, chips in the UK, etc.), while a semasiological question is, e.g., "what is the meaning of the term chips?" (answers: 'long, narrow pieces of potato that have been deep-fried' in the UK, 'slim slices of potatoes deep fried or baked until crisp' in the US).

Onomasiology can be carried out synchronically or diachronically, i.e. historically. The majority of linguists seem to link onomasiology automatically to diachronic questions, i.e. questions on how and why things change their names. Therefore, the following sections refer predominantly to onomasiology in its diachronic perspective.