In grammar, a supine is a form of verbal noun used in some languages. The term is most often used for Latin, where it is one of the four principal parts of a verb. The word refers to a position of lying on one's back (as opposed to 'prone', lying face downward), but there exists no widely accepted etymology that explains why or how the term came to be used to also describe this form of a verb.
Latin conjugation#Supine and Latin syntax#The supine
There are two supines, I (first) and II (second). They are originally the accusative and dative or ablative forms of a verbal noun in the fourth declension, respectively.
The first supine ends in -um. It has two uses.
The first supine comes with verbs of motion. In one usage, it indicates purpose:
'Mater pompam me spectatum duxit' is 'Mother took me to watch the procession'.
'Legati ad Caesarem gratulatum convenerunt' is 'The ambassadors came to Caesar to congratulate him'.
The translation of this first usage of the first supine is similar to, if not identical to, the Latin clause of purpose.
A second usage is in combination with the future passive infinitive. In this second usage it indicates fate; for example "occisum iri" means 'to be going to be killed'. It mostly appears in indirect statements:
' Occisum iri a Milone video' is 'I foresee that he is going to be killed by Milo'.
The second supine, which comes with adjectives, is rarely used; only a few verbs have been seen to commonly adopt the form. It is derived from the dative of purpose, which expresses the purpose of a thing or action, or the ablative of respect, which can translate as "with regard/respect to" and is used to indicate to what extent or in what way the main clause is true. It is the same as the first supine but replacing final -um by -ū, with a lengthened u. Mirabile dictū, for example, translates as "amazing to say", where dictū is the supine form. The sense is generally passive, even if usually not explicitly marked as such in idiomatic English translation; for example, difficile creditū, "hard to believe", is more literally "hard to be believed", or "hardly believable".