φύς

Etymology
Substantivization/nominalization of the participle.

Participle

 * : "(he) has sprung forth/been brought forth, (he) has been begotten, (he) has been born"

Noun

 * 1)  he who has sprung forth/been brought forth, he who has been begotten, he who has been born
 * 2)  son, (male) child, (male) descendant

Usage notes
The apparent IE root of the Ancient Greek verb, *bʰuh₂-, seems to have originally had the intransitive meanings "to appear/spring forth", "to grow/wax", "to become". Despite this, by the classical period assumed, in the present tense, both the transitive meanings "to bring forth" ("to produce", "to beget", "to engender"), and the intransitive meanings "to arise", "to emerge", "to spring up", "to grow". Often, Greek verbs with both transitive and intransitive meanings developed two aorist tenses: a first aorist (aorist 1) to assume the transitive meanings, and a second aorist (aorist 2) to assume the intransitive. Classical Greek second aorist tenses ending in -ην (e.g. βάινω/ἒβην), -ων (e.g. βιόω /ἐβίων), and -υν (e.g. δύομαι /ἒδυν) are generally intransitive. Accordingly, in the case of, a second aorist tense (second aorist ἔφῡν) arose to assume those intransitive meanings in the historical context. While the basic meanings of, the first aorist tense of , are identical with the transitive meanings of the present tense ("to bring forth", "to produce", "to cause to arise/appear", "to beget"), the basic meanings of second aorist are more in line with the intransitive meanings of φῠ́ω and of the presumed IE root, *bʰuh₂-. The instant participle, φῡ́ς, is the second aorist active masculine participle of the verb φῠ́ω, and so has essentially intransitive meanings in the active voice.

In the specific case of the substantivized aorist masculine participle, which clearly refers to a (male) person or persons, the essentially intransitive meaning of the second aorist took on meanings both markedly passive and more specific to the human condition ("to be begotten", "to be born"). Therefore, with respect to verb, the second aorist masculine participle can drastically differ in meaning from the first aorist masculine participle , and that, with respect to the basic meaning of verb , the (first aorist) active participle  can substantively represent the agent noun "father", and , in like manner an active participle, can substantively represent the result noun "son".