* ee - as in "see," "tree," "bee"
* ea - as in "sea," "meat," "bread"
* ie - as in "pie," "lie," "tie"
* ey - as in "key," "they," "monkey"
* y - as in "happy," "pretty," "city"
* i - as in "machine," "police," "believe"
* e - as in "here," "mere," "there"
There are other combinations of letters that can make the "ee" sound, but these are the most common.