Finite vs. nonfinite

Clauses or verbs in inflecting languages are often said to be finite or non-finite, which means that they either have or lack tense and/or person-number specifictions.

Term properties
The abstract noun is finiteness.

Examples
In Latin, finite forms are forms such as am-o 'I love', ama-s 'you love', ama-t 's/he loves'. Nonfinite forms are the infinitive amare 'to love' and the participle amatus 'loved (one)'.

Comments
The term pair originally comes from the grammar of Indo-European languages, where finite verbs generally either have both tense and person-number specifications, or lack both tense and person-number specifications. For this reason, it is unclear how to apply the terminology when a verb form lacks tense but has person-number specifications (like the Portuguese conjugated infinitive), or when it lacks person-number but has tense.

Due to this impreciseness, a number of linguists have suggested that the terminology should be abandoned entirely in cross-linguistic contexts. For Indo-European languages, the term tensed has often been used instead in recent times.

Origin
Latin finitus (from finire 'finish') means 'finished', but also 'determined', 'specified'. Finite forms are thus called because they are specified for tense and person-number. The term pair was apparently created on the basis of the older term infinitive. It has been in use only since the 19th century. An early use is in Murray (1798).

Other languages
German finit vs. infinit