でもある

でもある means "is also": the subject is one thing already, and this adds another role or quality. It goes straight after a noun or a な-adjective, as である does, with も slipped in.

The first role often comes first with であり, and でもある adds the second: "is A, and is also B".

は…でもある or も…だ

Where も goes decides what is "also". After the subject, it adds another person or thing to the same description. Inside でもある, it adds another description to the same subject.

• × 彼も医者だ (meaning he has a second job) → 彼は医者でもある

Usage notes

These go beyond the plain written form.

Polite form

である is the written copula, so でもある reads as written style. Polite speech uses でもあります.

い-adjectives

An い-adjective changes its い to く and takes もある: たのしく楽しくもある.