Learn Icelandic: Ég var þreyttur og gleymdi að lesa tölvupóstinn. - I was tired and forgot to read the email.

gleymdi is the past tense of the verb gleyma (to forget). This is a weak verb, which means it forms the past tense by adding a suffix like -di, -ti, or -ði instead of changing its core vowel. For gleyma, the stem ends in the letter m, so it takes the -di ending to mean 'I forgot'.

Does the word þreyttur tell us anything about the speaker?

Yes, it tells us the speaker is male. The adjective þreyttur means 'tired' and is in the masculine singular form. If the speaker were female, she would drop the -ur ending and say ég var þreytt.

Why do we need the word að before lesa?

The word að works just like 'to' does in the English phrase 'to read'. When you connect a main verb like gleymdi to a secondary action, that second verb stays in its basic dictionary form (the infinitive) and needs the infinitive marker að right in front of it.

How does the word tölvupóstinn include the word 'the'?