definiens

English

From Latin, substantive use of dēfīniēns (“[a] defining”), present active participle of dēfīniō.

(Received Pronunciation) IPA^(key): /dɪˈfɪnɪɛnz/^[1], /deːˈfiːnieːns/, /diːˈfaɪnɪɛːnz/
Audio (Southern England): (file)

Examples
A lake is a large, landlocked, naturally occurring stretch of water.

definiens (plural definientia)

(semantics) The word or phrase that defines the definiendum in a definition.
- 1977, Nelson Goodman, The Structure of Appearance, 3rd edition, D. Reidel, →ISBN, page XLIV:
  Yet such predicates will not in general even be interpreted over the domain of objects over which the definientia range.
- 2011, Michail Peramatzis, Priority in Aristotle's Metaphysics, Oxford University Press, →ISBN, page 196:
  In these definitions, then, there is only one part of the definiens, the form (e.g. being a human soul), which is prior to the kind and its matter.

Present participle of dēfīniō.

dēfīniēns (genitive dēfīnientis); third-declension one-termination participle

Case / Gender	Masc./Fem.	Neuter	Masc./Fem.	Neuter
Number	Singular		Plural
Nominative	dēfīniēns		dēfīnientēs	dēfīnientia
Genitive	dēfīnientis		dēfīnientium
Dative	dēfīnientī		dēfīnientibus
Accusative	dēfīnientem	dēfīniēns	dēfīnientēs dēfīnientīs	dēfīnientia
Ablative	dēfīniente dēfīnientī¹		dēfīnientibus
Vocative	dēfīniēns		dēfīnientēs	dēfīnientia

¹When used purely as an adjective.