Lexicology is the part of linguistics which studies words. This may include their nature and function as symbols their meaning, the relationship of their meaning to epistemology in general, and the rules of their composition from smaller elements (morphemes such as the English -ed marker for past or un- for negation; and phonemes as basic sound units). Lexicology also involves relations between words, which may involve semantics (for example, love vs. affection), derivation (for example, fathom vs. unfathomably), usage and sociolinguistic distinctions (for example, flesh vs. meat), and any other issues involved in analyzing the whole lexicon of a language(s).
The term first appeared in the 1820s, though there were lexicologists in essence before the term was coined. Computational lexicology as a related field (in the same way that computational linguistics is related to linguistics) deals with the computational study of dictionaries and their contents.
An allied science to lexicology is lexicography, which also studies words, but primarily in relation with dictionaries – it is actually concerned with the inclusion of words in dictionaries and from that perspective with the whole lexicon. Sometimes lexicography is considered to be a part or a branch of lexicology, but properly speaking, only lexicologists who actually write dictionaries are lexicographers. Some consider this a distinction of theory vs. practice.
The word "lexicology" derives from the Greek "λεξικόν" (lexicon), neut. of "λεξικός" (lexikos), "of or for words", from "λέξις" (lexis), "speech", "word", (in turn from "λέγω" lego "to say", "to speak") + "-λογία", (-logia), "the study of", a suffix derived from "λόγος" (logos), amongst others meaning "speech, oration, discourse, quote, study, calculation, reason", it turn also from "λέγω".
Lexical semantics 
Semantic relations between words are of many kinds, for example homonymy, antonymy, meronymy, and paronymy. Semantics as specifically involved in lexicological work is called lexical semantics. Lexical semantics is somewhat different from the semantics of larger units such as phrases, sentences, and complete texts (or discourses), because it does not involve the same degree of compositional semantics complexities; however, the notion of "word" can be extremely complex, particularly in agglutinative languages.
Outside but related to linguistics, other forms of semantics are studied, such as cultural semantics and computational semantics (the latter may refer either to computational lexicology or mathematical logic.
Lexical semantics may not be understood without a brief exploration of its history.
Prestructuralist semantics 
Semantics as a linguistic discipline has its beginning in the middle of the 19th century, and because linguistics at the time was predominantly diachronic, thus lexical semantics was diachronic too – it dominated the scene between the years of 1870 and 1930. Diachronic lexical semantics was interested without a doubt in the change of meaning with predominantly semasiological approach, taking the notion of meaning in a psychological aspect: lexical meanings were considered to be psychological entities), thoughts and ideas, and meaning changes are explained as resulting from psychological processes.
Structuralist and neostructuralist semantics 
With the rise of new ideas after the ground break of Saussure's work, prestructuralist diachronic semantics was considerably criticized for the atomic study of words, the diachronic approach and the mingle of nonlinguistics spheres of investigation. The study became synchronic, concerned with semantic structures and narrowly linguistic structures.
Semantic structural relations of lexical entities can be seen in three ways:
- semantic similarity
- lexical relations such as synonymy, antonymy, and hyponymy
- syntagmatic lexical relations were identified
Chomskyan school 
Followers of Chomskyan generative approach to grammar soon investigated two different types of semantics, which, unfortunately, clashed in an effusive debate, these were interpretative and generative semantics.
Cognitive semantics 
Cognitive lexical semantics is thought to be most productive of the current approaches.
Another branch of lexicology, together with lexicography is phraseology. It studies compound meanings of two or more words, as in "raining cats and dogs". Because the whole meaning of that phrase is much different from the meaning of words included alone, phraseology examines how and why such meanings come in everyday use, and what possibly are the laws governing these word combinations. Phraseology also investigates idioms.
Since lexicology studies the meaning of words and their semantic relations, it often explores the origin and history of a word, i.e. its etymology. Etymologists analyse related languages using a technique known as the comparative method. In this way, word roots have been found that can be traced all the way back to the origin of, for instance, the Proto Indo-European language.
Etymology can be helpful in clarifying some questionable meanings, spellings, etc., and is also used in lexicography. For example, etymological dictionaries provide words with their historical origins, change and development.
A familiar example of lexicology at work is that of dictionaries and thesauri. Dictionaries are books or computer programs (or databases) that actually represent lexicographical work, they are opened and purposed for the use of public.
As there are many different types of dictionaries, there are many different types of lexicographers.
Questions that lexicographers are concerned with are for example the difficulties in defining what simple words such as 'the' mean, and how compound or complex words, or words with many meanings can be clearly explained. Also which words to keep in and which not to include in a dictionary.
Noted lexicographers 
Some noted lexicographers include:
- Dr. Samuel Johnson (September 18, 1709 – December 13, 1784)
- French lexicographer Pierre Larousse (October 23, 1817-January 3, 1875)
- Noah Webster (October 16, 1758 – May 28, 1843)
- Russian lexicographer Vladimir Dal (November 10, 1801 – September 22, 1872)
- Damaso Alonso, (Oct. 22, 1898-) Spanish literary critic and lexicologist
- Roland Barthes, (Nov. 12, 1915-Mar. 25, 1980) French writer, critic and lexicologist
- Lexicology/Lexikologie: International Handbook on the Nature and Structure of Words and Vocabulary/Ein Internationales Handbuch Zur Natur and Struktur Von Wortern Und Wortschatzen, Vol 1. & Vol 2. (Eds. A. Cruse et al.)
- Words, Meaning, and Vocabulary: An Introduction to Modern English Lexicology, (ed. H. Jackson); ISBN 0-304-70396-6
- Toward a Functional Lexicology, (ed. G. Wotjak); ISBN 0-8204-3526-0
- Lexicology, Semantics, and Lexicography, (ed. J. Coleman); ISBN 1-55619-972-4
- English Lexicology: Lexical Structure, Word Semantics & Word-formation,(Leonhard Lipka.); ISBN 978-3-8233-4995-2
- Outline of English Lexicology , (Leonhard Lipka.); ISBN 3-484-41003-5
See also 
- Phono-semantic matching
- List of lexicographers
- List of linguists
- Computational lexicology
- English lexicology and lexicography
- Analysis of subjective logics
- Willard Van Orman Quine, Word and Object, 1960.
- λεξικός, Henry George Liddell, Robert Scott, A Greek–English Lexicon, on Perseus Digital Library
- λέξις, Henry George Liddell, Robert Scott, A Greek–English Lexicon, on Perseus Digital Library
- λέγω, Henry George Liddell, Robert Scott, An Intermediate Greek–English Lexicon, on Perseus Digital Library
- λόγος, Henry George Liddell, Robert Scott, A Greek–English Lexicon, on Perseus Digital Library
- Dirk Geeraerts, The theoretical and descriptive development of lexical semantics, Prestructuralist semantics, Published in: The Lexicon in Focus. Competition and Convergence in Current Lexicology, ed. Leila Behrens and Dietmar Zaefferer, p. 23–42
- Dirk Geeraerts, The theoretical and descriptive development of lexical semantics, Structuralist and neostructuralist semantics, Published in: The Lexicon in Focus. Competition and Convergence in Current Lexicology, ed. Leila Behrens and Dietmar Zaefferer, p. 23–42
- Harris, Randy Allen (1993) The Linguistics Wars, Oxford, New York: Oxford University Press
|Look up lexicology in Wiktionary, the free dictionary.|
- Association for Automatic Language Processing (ATALA), Paris, France
- International Society for Historical Lexicography and Lexicology, University of Leicester
- 'L' entries (from lexeme to lexicon) at SIL (Summer Institute of Linguistics)'s glossary of linguistic terms