Henotheism means you only worship one God, but you believe there are many gods.
The first commandment of the ten commandments illustrates that Judaism is Henotheistic, not Monotheistic. Monotheism means you only believe there is one God.
Thou shalt have no other gods before me. (Exodus 20:3, Deuteronomy 5:7)
This verse says there are other gods.
Even Christianity is henotheistic. There are other gods; not called gods, but rather called angels and demons and such. They have the same kinds of attributes and powers as the gods of polytheism, but they are not named gods (but should be).