Nauta _________ (a good sailor) bona bonus bonum bonae?

Question

PLease help me. I marked bona and got the answer wrong. I don't understand?

Answer 1

If Nauta is wrong, that's because Nauta is masculine. So, you have to mark Bonus.

Even in the first declination there are some words in -a which are masculine.

Latin words which end with "-a" are usually feminine, but in the past only men used to be Nauta (sailors), so Nauta is masculine. The same for "Agricola".

Answer 2

Thus far the adjectives have had the same terminations as the nouns. However, the agreement between the adjective and its noun does not mean that they must have the same termination. If the adjective and the noun belong to different declensions, the terminations will, in many cases, not be the same. For example, «nauta», sailor, is _masculine_ and belongs to the first declension. The masculine form of the adjective «bonus» is of the second declension. Consequently, 'a good sailor' is _«nauta bonus»_. So, 'the wicked farmer' is «agricola malus».

«nauta bonus» m., 'the good sailor'