Indefinite article used before a noun to indicate a single item.

एक अदृश्य

English Usage: "I saw a bird in the tree."

Hindi Usage: "मैंने पेड़ में एक पक्षी देखा।"

Used informally to mean "one" or "any."

एक

English Usage: "It's a nice place to visit."

Hindi Usage: "यह जाने के लिए एक अच्छा स्थान है।"

Used as a short form for 'and' in informal contexts.

और

English Usage: "I like tea a coffee."

Hindi Usage: "मुझे चाय और कॉफी पसंद है।"

Rarely used as a verb to indicate a state of being.

होना

English Usage: "It will a lovely day."

Hindi Usage: "यह एक प्यारा दिन होगा।"