Definition from Wiktionary, the free dictionary
- then, at that time (demonstrative correlative of time)
Usage notes 
- As with other demonstrative correlatives in Esperanto, tiam can be combined with ĉi, the adverbial particle of proximity, or with for, the adverbial particle of distance. Tiam ĉi thus means then [recently or soon] and tiam for means then [long ago or in distant future].