En or Ett?

In Swedish, the noun is either n-genus (common gender) or t-genus (neuter). As a native Swede, you learn this when you grow up. It is more difficult for those who want to learn Swedish as a foreign language.

In general, living beings are n-words. But there are exceptions, e.g. child (barn) and lion (lejon) that are t-words. In short, there are no fixed rules for this.

In Swedish, you use the articles 'en' or 'ett' before nouns. They are both the same word as the numeral 'one'. Since you can't clearly tell from the noun when to use 'en' or 'ett' for it, you simply have to learn and remember which one it is.

'En' (common gender) is more common than 'ett' (neuter) for some reason that dates so far back in time that no one knows why anymore.