Learn Icelandic: Þetta er góð mynd. - This is a good picture.

The adjective must match the gender of the noun it describes. The noun mynd is feminine, so we use the feminine singular form góð. If the noun were masculine, it would be góður, and if neuter, it would be gott.

If mynd is feminine, why does the sentence start with the neuter word þetta instead of the feminine þessi?

In Icelandic, when you use the phrase 'This is a...' or 'That is a...', the pointer word always takes the default neuter form (þetta) no matter what the gender of the following noun is. However, any adjectives attached directly to the noun still have to match its gender, which is why we use góð.

Why do we use the 'strong' adjective form here?

Adjectives use the strong declension when the noun they describe is indefinite, meaning it does not have the definite article ('the') attached to it. Since we are saying 'a good picture' rather than 'the good picture', we use the strong feminine form góð.

Can mynd mean anything else besides 'picture'?

Yes! While it literally means 'picture', 'image', or 'drawing', it is also the most common word for a 'movie' or 'film' in Icelandic. Depending on what you are talking about, this sentence could easily mean 'This is a good movie.'