Other forms: tends, tended, tending
To tend is to be likely to do something, as a habit. It usually happens, and there are exceptions.
It takes to and a verb, and it is one of the most useful hedges in English, since saying that people tend to arrive late claims a pattern without claiming a rule. Academic writing depends on it. There is a completely separate verb meaning to look after, so tending a garden or tending the sick is care rather than probability, and a bartender tends a bar.
Tend is attend with the front worn off. Middle English tenden meant to pay attention to, cut down from attenden or entenden, which is why tending a fire and tending to agree are one word.
Proto-Indo-European
*tend-
Middle English
tenden
English, today
tend
From Middle English tenden. From Middle English tenden, from Middle French tendre, from Old French tendre (“to stretch, stretch out, hold forth, offer, tender”), from Latin tendere (“to stretch, stretch out, extend, spread out”).
Etymology from Wiktionary, CC BY-SA