coesyn yr ymennydd

Noun

 * 1) the brain stem

Usage notes

 * The two nouns that form this term are in a genitive construction, with the first noun being definite by default. Determiners precede the second second noun . When the second noun is indefinite or its definiteness can be inferred from a possessive pronoun or a genitive relationship to another noun, the definite article is dropped as is usual in Welsh: