Learn Hardcore Icelandic: Sendu mér símanúmerið, vinsamlegast.

It’s the second-person singular imperative of að senda (to send). Imperatives give direct instructions: Sendu = “(You) send!” The plural imperative is Sendið (“You all send!”). Using vinsamlegast (“please”) softens the command.

Why is it mér and not mig?

Icelandic marks the recipient of “sending” in the dative case: senda e-m e-ð (“send something to someone”). Mér is the dative of “I” (ég). Mig is the accusative and would be used if “me” were the direct object (e.g., “send me [as the thing]”). So: Sendu mér símanúmerið = “Send the phone number to me.”

What does the ending -ið in símanúmerið mean?

It’s the attached definite article for neuter nouns (“the”). Símanúmer = “phone number”; símanúmerið = “the phone number.” Here it’s the direct object, so it’s in the accusative neuter singular, which looks the same as nominative in neuter.

Is símanúmer a compound word?

Yes. It’s síma- (the genitive form of sími, “telephone”) + númer (“number”). The head is númer, which is neuter; the definite article attaches to the end: símanúmerið. Icelandic compounds are written as one word (no hyphen): , not “síma númer” or “síma-númer.”