li

As a noun null is

zero, nil; the cardinal number before einn.

As a letter s

is the letter s with a.

As an adverb na is

already, now.

As a proper noun lithium

is a village in missouri.

As a noun ly

is reason.

As a proper noun roof

is (astronomy) a chinese constellation located near aquarius and pegasus, one of the 28 lunar mansions and part of the larger black turtle.