Esperanto has a definite article la. The article is alike for all cases and number. There is no indefinite article. The usage of the definite article is similar to the usage of definite articles in western languages.
If the article is preceded by a preposition ending with a vowel, the final a of the article can be dropped and replaced by an apostrophe: la amo de la patrino = la amo de l’patrino^H – the love of the mother. Rarely, mostly in poetry, the elision occurs also in other cases if it is possible to pronounce it: L' espero, l'obstino kaj la pacienco...^[4] – Hope, stubbornness and patience...

^[4] Cited from PMEG, however originally from Zamenhof, L: Fundamenta Krestomatio de la Lingvo Esperanto, p.300