tact

*in-* (not) + *tact* (touched) = "untouched." The logic is wonderfully physical: a thing nobody has laid a finger on hasn't been broken, scratched, or rearranged — so it's whole and undamaged. That's why intact almost always implies survival through some threat: the building was intact after the storm; her reputation remained intact. Note it has no comparative — something is intact or it isn't.

*con-* (together) + *tag* (touch) + *-ous* = "spreading by touching together." The original idea is alarmingly literal: a disease that jumps the moment one body touches another. English then lent it to anything that spreads person-to-person — a contagious laugh, contagious enthusiasm. Compare its cousin contagion (the noun for the spread itself) and contiguous (just touching, no spreading).

The family's biggest leap. *con-* (together) + *ting-* (touch) literally meant things "touching together" — and what touches you by chance is what merely happens to you. So contingent came to mean "dependent on circumstances, possible but not certain": your bonus is contingent on results. As a noun it also names a group sent to represent a larger body (a military contingent). The noun contingency is the uncertain event you prepare for — hence contingency plan.

Pure metaphor: the sense of touch applied to people. Just as your fingertips read a surface without looking, tact is reading a social situation by feel — sensing what will hurt and steering around it. That's why we say someone "handles" a delicate matter with tact. tactful is the adjective, tactless its blunt opposite. Don't confuse it with tactic/tactical, which look identical but come from Greek taktikos (arrangement of troops), an unrelated root.