het is a feminine noun. Adjectives undergo soft muation following a feminine noun.

There are several rough guidelines, but they tend come with lists of exceptions, many of which are common nouns. To begin with you may find it better just to learn them by rote, then perhaps look at some of the guidelines that you will find on the web to see how useful or not you think they are.

As an example, singular nouns ending -en tend to be feminine - but bachgen is one of the common exceptions. Multi-syllable -aeth nouns are nearly all feminine - but not gwasanaeth, gwahaniaeth and a few others.

A few nouns also change gender depending on dialect and region, some very locally - tafarn can sometimes be found as a masculine noun in mid-Glamorgan. A few nouns have different genders, and occasionally different plurals, for different meanings - llif, for example.

You are right that ‘blue’ is glas. However, adjectives take a soft mutation if they follow a feminine noun such as het:

• car glas - a blue car (car is a masculine noun, so glas does not mutate)
• het las - a blue hat (het is a feminine noun, so glas has to mutate to las)

Mmm, but I'm a native speaker and know that you are allowed to say "las". Also, I was born in Cardiff too, so maybe your family are from the North and know things differently?

Mmm, but I'm a native speaker and know that you are allowed to say "las". Also, I was born in Cardiff too, so maybe your family are from the North and know things differently?

Mmm... but I'm a native speaker and know that you are allowed to say "las". Also, I was born in Cardiff too, so maybe your family are from the North and know things differently?