The word namaste, pronounced “NUHM-uh-stay,” is a common Hindu/Indian greeting often used in conjunction with a small bow and with the palms of one’s hands placed together, fingers up, in front of the chest. In Indian culture, it is used casually. With some aspects of Hindu/Indian culture becoming increasingly popular in other parts of the world, yoga for example, the use of namaste is increasing in popularity as well.
A Christian should not say or do anything that originates from a different religion without first examining its meaning and origin. While to a Hindu namaste can be used as casually as “good morning,” the word itself literally means “I bow to you.” Culturally, it has come to mean “I bow to the god in you” and more fully “the god in me bows to the god in you.”
The saying of namaste is incompatible with the Christian faith. Human beings are not gods. There is only one God, and He does not share His glory (Isaiah 42:8). Bowing to or showing any sort of respect to any false god is idolatry (Exodus 20:3). Depending on the version of Hinduism, Hindu beliefs are polytheistic or pantheistic or a mixture of both. Namaste seems to come from the more pantheistic forms of Hinduism that see everything and everyone as god.
Whether you actually intend to communicate the literal meaning of namaste is irrelevant. Would you say, “You are a god; I bow to you” to someone in English? Neither should you say a word that means precisely that in Hindi, Nepali, or any other language.