Semasiology (from — indicate, signify) is discipline within linguistics 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 senses, i.e. polysemy. The opposite approach is known as onomasiology.
The term was first used by Christian Carl Reissig in 1825 in his Vorlesungen über lateinische Sprachwissenschaft (E. Lectures on Latin Linguistics).
The discipline is most commonly understood as a branch of lexicology, the study of words, and as a branch of semantics, and more narrowly ascribed as a subfield of lexical semantics, though sometimes referred as a semantics' synonym. The 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.
semasiology in Estonian: Semasioloogia
semasiology in Ukrainian: Семасіологія
semasiology in Slovak: Semasiológia