OTRO is the thirtieth most common word in the Spanish language. OTRA is the singular feminine form, with OTROS and OTRAS being the corresponding masculine and feminine forms in the plural.
OTRO is described in my Collins English-Spanish dictionary as both a noun and a pronoun.
OTRO has a number of shades of meaning, but the key translations are “other” or “another”.
Here are some examples of its use:-
necesito otro diccionario
¡otra! – encore!
This last example is the mongrel language English at its best! I have used a French word (encore – literally meaning again) to translate a Spanish word. English certainly is predatory and collects and assimilates useful words wherever it can find them.
So there we have it – the thirtieth most common word in Spanish. Make sure you know it, can recognise it, and can use it!