Reading this question and its accepted answer prompted me to ask the following question:
Is there a difference between Suttas and Sutras? and, if so, what is the difference?
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Sutra (Skt.), Sutta (Pali) is a term for any literary composition. https://en.wikipedia.org/wiki/Sutra should get you started.
The word was in use in India before Buddhism, so you can find it used in all Indic religions (Hinduism, Buddhism, Jainism) as well as in Sanskrit grammar and poetry.
As with anything from as far back as two millenia, there's dissenting opinions, for example:
Some scholars consider that the Buddhist use of sutra is a faulty Sanskritization of the Prakrit or Pali word sutta and that the latter actually represented Sanskrit sūkta, "well spoken, good news"
SOURCE: K. R. Norman: A philological approach to Buddhism: the Bukkyo Dendo Kyokai Lectures 1994. (Buddhist Forum, Vol. v.) xx, 193 pp. London: School of Oriental and African Studies, 1997. p. 104
alpākṣaraṃ asandigdhaṃ sāravad viśvatomukham astobhaṃ anavadyaṃ ca sūtram sūtravido viduḥ.
Of minimal syllabary, unambiguous, pithy, comprehensive, continuous, and without flaw: who knows the sutra knows it to be thus.
SOURCE: Vayu Purana