Translation guide
The word 'lexicon' refers to the vocabulary of a language, a person, or a specialized field. In Japanese, different terms are used depending on whether you mean a dictionary-like list, the mental vocabulary, or the vocabulary of a particular domain.
Referring to the entire set of words in a language or a specialized domain.
The most common and general term for 'vocabulary' or 'lexicon'. It can refer to the words of a language, a person, or a field.
The Japanese lexicon is rich.
I need to expand my technical lexicon.
Specifically a glossary or collection of terms, often for a specific field. More like a 'terminology list' than a mental lexicon.
This medical lexicon is useful.
Means 'dictionary'. Sometimes used loosely to refer to a lexicon as a reference work, but it's not the mental lexicon.
He is a walking lexicon.
Referring to the words that a particular person knows or uses.
Same word as above, but used in the context of an individual's vocabulary.
She has a rich lexicon.
Reading expands your lexicon.
Loanword from English, often used in educational contexts or casual speech. Slightly more colloquial than 語彙.
Referring to a physical or digital book that lists words and their meanings.
Standard word for dictionary. Can be used for any language.
I consult an English-Japanese lexicon.
Often used in titles of dictionaries, especially specialized ones. Slightly more formal than 辞書.
Older, colloquial term for dictionary. Literally 'character puller'. Rarely used today.
Referring to the mental repository of words and their properties in linguistic theory.
語彙 (ごい) refers to vocabulary or the mental lexicon, while 辞書 (じしょ) is a physical or digital dictionary. Don't use 辞書 when you mean someone's vocabulary.
His lexicon is amazing.
I look up words in a lexicon (dictionary).
I want to increase my lexicon.
I bought a Japanese lexicon.
Look it up in the lexicon.