"Elephants are big animals."
Translation:हाथी बड़े जानवर होते हैं ।
Be careful, a word ending in ी is not necessarily female, and a word ending in ा is not necessarily male. हाथी is male, and as such the plural is the same (also हाथी). The general pluralizing scheme is:
Male ending in ा -> े (लड़का -> लड़के)
Male not ending in ा -> No change (हाथी -> हाथी)
Female ending in ी -> ियाँ (लड़की -> लड़कियाँ)
Female not ending in ी -> add ें (गाय -> गायें)
Be careful because sometimes you will see other forms (दोस्त -> दोस्तों) but this has to do with the oblique form, and is something different.