Semasiology is a discipline within linguistics

Linguistics

Linguistics is the scientific study of human language. Linguistics can be broadly broken into three categories or subfields of study: language form, language meaning, and language in context....

 concerned with the question "what does the word X mean?". It studies the meaning of words regardless of their phonetic expression. Semasiology departs from a word or lexical expression and asks for its meaning, its different sense

Sense

Senses are physiological capacities of organisms that provide inputs for perception. The senses and their operation, classification, and theory are overlapping topics studied by a variety of fields, most notably neuroscience, cognitive psychology , and philosophy of perception...

s, i.e. polysemy

Polysemy

Polysemy is the capacity for a sign or signs to have multiple meanings , i.e., a large semantic field.Charles Fillmore and Beryl Atkins’ definition stipulates three elements: the various senses of a polysemous word have a central origin, the links between these senses form a network, and ...

. The opposite approach is known as onomasiology

Onomasiology

Onomasiology 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 .Onomasiology, as a part of lexicology, starts from a concept which is taken to be priorOnomasiology (from — to name,...

.

The term was first used by Christian Karl Reisig

Christian Karl Reisig

Christian Karl Reisig was a German philologist and linguist who was a native of Weissensee, Thuringia....

 in 1825 in his Vorlesungen über lateinische Sprachwissenschaft (E. Lectures on Latin Linguistics).

The discipline is most commonly understood as a branch of lexicology

Lexicology

Lexicology is the part of linguistics which studies words, their nature and meaning, words' elements, relations between words , word groups and the whole lexicon....

, the study of words, and as a branch of semantics

Semantics

Semantics is the study of meaning. It focuses on the relation between signifiers, such as words, phrases, signs and symbols, and what they stand for, their denotata....

, and more narrowly ascribed as a subfield of lexical semantics

Lexical semantics

Lexical semantics is a subfield of linguistic semantics. It is the study of how and what the words of a language denote . Words may either be taken to denote things in the world, or concepts, depending on the particular approach to lexical semantics.The units of meaning in lexical semantics are...

, though sometimes referred to as a synonym

Synonym

Synonyms are different words with almost identical or similar meanings. Words that are synonyms are said to be synonymous, and the state of being a synonym is called synonymy. The word comes from Ancient Greek syn and onoma . The words car and automobile are synonyms...

 of semantics

Semantics

Semantics is the study of meaning. It focuses on the relation between signifiers, such as words, phrases, signs and symbols, and what they stand for, their denotata....

. The exact meaning of the term is somewhat obscure, because according to some authors semasiology merged with semantics in modern times, while at the same time the term is still in use when defining onomasiology

Onomasiology

Onomasiology 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 .Onomasiology, as a part of lexicology, starts from a concept which is taken to be priorOnomasiology (from — to name,...

.