invariable

sifat adjective

1. (by extension, grammar, of a word, or a grammatical class) That cannot undergo inflection, conjugation or declension. The French adjective marron (brown) is invariable: it does not take the usual s in the plural.
2. Not variable; unalterable; uniform; always having the same value.
3. Constant.

ot noun

1. Something that does not vary; a constant.