Mental means happening in the mind rather than the body. Mental arithmetic is the sum you do in your head; a mental note is the thing you tell yourself to remember and then forget by the afternoon.
The pairing you meet most is mental health — how a person is doing inside, discussed now as plainly as a bad back. Mental illness and mentally ill belong to the medical and older institutional vocabulary, and calling somebody a mental patient is offensive; say a person has a mental health condition. In informal British speech, mental also means wild or mad — the crowd went mental, it was mental in town on Saturday — and calling a person mental is an insult, so keep that use for the party and not for the person. The adverb is mentally: mentally exhausted, mentally I had already left the room.
1adjectivementalHappening in the mind, or connected with the mind.~36%
“Mental arithmetic was the only part of the test he enjoyed.”
synonyms: cognitive
2adjectiveillnessesConnected with illnesses and conditions of the mind.~62%
“The company finally brought in proper mental health support.”
3adjectivewildWild, crazy or furious, in informal British English.~2%
“The crowd went mental when the second goal went in.”
Shares are an estimate: a language model read 11 sentences found in the wild and placed 11 of them on a sense — a count of our sample, not a measurement of English.
Middle French mental came from Latin mentālis, built on mēns with the adjective ending -ālis, and behind it stands the Proto-Indo-European root *men-. That -ālis is doing the job every English -al still does: turning a noun into a word that describes.
Proto-Indo-European
*men-
Latin
mentālis
Middle French
mental
English, today
mental
Borrowing from Middle French mental, from Latin mentālis, from mēns + -ālis.
Etymology from Wiktionary, CC BY-SA