Ap (áp-) is the Vedic Sanskrit term for "water", in Classical Sanskrit occurring only in the plural, āpas (sometimes re-analysed as a thematic singular, āpa-), whence Hindi āp. The term is from PIE hxap "water". The Indo-Iranian word survives also, as the Persian word for water, Āb, e.g. in Punjab (from panj-āb "five waters"). In archaic ablauting contractions, the laryngeal of the PIE root remains visible in Vedic Sanskrit, e.g. pratīpa- "against the current", from *proti-hxp-o-.