"EVERYDAY" vs ''EVERY DAY"

These sentences are all wrong:

1. He comes everyday.
2. We eat everyday.
3. They play everyday.

The one word "everyday" is an Adjective. It must go with a Noun.
e.g.
1. This is an everyday matter.
(matter = Noun; everyday = Adjective)
2. She was in her everyday dress.
(dress = Noun; everyday = Adjective)
3. This is everyday talk.
(talk = Noun)
4. We speak to friends in everyday language.

"Every day" is used as an Adverb. It is therefore used with a verb.
e.g.
1. He comes every day.
2. She sings every day.
3. You read every day.

Another point to remember is that "every' is an Adjective that is used with Singular nouns, that is, with one thing or person.
e.g.
1. He comes every Sunday.
2. Every boy must go to school.