あなたがいなくて淋しいです。

you (referring to someone of equal or lower status); dear (what a wife calls a husband)

indicates sentence subject (occasionally object); indicates possessive (esp. in literary expressions); but; however; still; and

to be (of animate objects); to exist; to stay; (after the -te form of a verb) verb indicating continuing action or state (i.e. to be ..ing, to have been ..ing)

lonely; lonesome; solitary; desolate

be; is