Tact is the skill of handling people carefully — knowing what to say, how to say it, and often what to leave out, so that nobody ends up hurt, embarrassed or made to look foolish. It shows up most in difficult moments: telling someone bad news, refusing an invitation, correcting a colleague, or mentioning something awkward about how a person looks or behaves.

It is worth seeing what tact actually is, because it is easy to mistake it for simply being nice. Tact is a judgement, made quickly, about another person's feelings — reading the room, sensing what this particular person can hear right now, and shaping your words to fit. That is why English says someone 'has tact', as though it were an ability, and why the opposite, tactless, sounds like a real failing rather than mere rudeness. A rude person meant to wound; a tactless person often meant well and simply did not think.

It is uncountable: you have tact, you show tact, you handle something with tact, you need tact, and you can do something with great tact. You cannot say 'a tact' or 'two tacts'. The phrase 'with tact' is very common, and so is the pairing 'tact and diplomacy', which turns up constantly in job advertisements — a polite way of saying the work involves difficult people.

There is a small piece of history hiding in the word. Tact first meant the sense of touch, and that older meaning explains the modern one exactly: a person with tact has a light touch with other people's feelings, handling a delicate situation the way you would handle something fragile. English still says 'a delicate matter' and 'handle it gently' for the same reason.