Just context (I think). Mostly derived from how the subject of the sentence is written. "He 'eats' an apple" and "He 'has' an apple". I think the 'He' part changes. From phonetic 'On yest' to 'Emu yest'. Don't take my word for it tho.
The same. The idea of definite and indefinite nouns is mostly communicated by context and word order. Here, you only have to rely on the context to pick the right English translation. Without it, both are fine.