There are two important things to take away from today’s Lexember words.
The first is the distinction between iê and ieth, which is etymologically vast, but for practical purposes is the same as the distinction between a and an in English, or knowing when to use le or l’ – or any other kind of liaison – in French. There are a lot of these sorts of words with alternate pre-vocalic forms, though this is the only one (so far) in which the two forms come from completely different sources.
The second important takeaway is that of the clausal versus phrasal conjunction. These are not interchangeable: iê and ieth must always be accompanied by a verb and join two clauses, while que connects two words in the same clause (usually nouns). It can help to think of iê and ieth as equivalent to “and then” while que is closer to “and also.”