Learn Icelandic: Er peysan of þröng? - Is the sweater too tight?

No, when of is used as an adverb of degree meaning 'too' (as in 'too tight'), it never changes its form. It always stays exactly like this and is placed directly before the adjective.

Can I use of to mean 'too' in the sense of 'also' or 'me too'?

No, of is only used as an adverb of degree to indicate excess (like 'too much' or 'too big'). If you want to say 'too' meaning 'also' (as in 'I want to go, too'), you must use the word líka.

Why is the adjective þröng instead of the dictionary form þröngur?

Adjectives must match the gender of the noun they describe. The word for sweater, peysa, is a feminine noun. Therefore, the adjective takes the feminine singular form þröng. If you were talking about a masculine noun like a shoe (skór), you would use the masculine form and say of þröngur.

Why is it peysan and not just peysa?

In Icelandic, the word for 'the' (the definite article) is attached to the end of the noun rather than being a separate word. Peysa means 'a sweater', and adding the feminine definite ending -n turns it into peysan, meaning 'the sweater'.