The difference between Purpose and Topic

When used as nouns, purpose means an object to be reached, whereas topic means subject.

Purpose is also verb with the meaning: to have set as one's purpose.

Topic is also adjective with the meaning: topical.

check bellow for the other definitions of Purpose and Topic

Purpose as a noun:

An object to be reached; a target; an aim; a goal. "purpose".
Purpose as a noun:

A result that is desired; an intention.
Purpose as a noun:

The act of intending to do something; resolution; determination.
Purpose as a noun:

The subject of discourse; the point at issue.

Examples:

"rfquotek Spenser"
Purpose as a noun:

The reason for which something is done, or the reason it is done in a particular way.

Examples:

"The purpose of turning off the lights overnight is to save energy."
Purpose as a noun (obsolete):

Instance; example.

Purpose as a verb (intransitive):

To have set as one's purpose; resolve to accomplish; intend; plan.
Purpose as a verb (transitive, passive):

To design for some purpose.
Purpose as a verb (obsolete, intransitive):

To discourse.

Examples:

"rfquotek Edmund Spenser"

Topic as a noun:

Subject; theme; a category or general area of interest.

Examples:

"A society where a topic cannot be discussed, does not have free speech."
Topic as a noun (Internet):

Discussion thread.
Topic as a noun (obsolete):

An argument or reason.
Topic as a noun (obsolete, medicine):

An external local application or remedy, such as a plaster, a blister, etc.

Examples:

"rfquotek Wiseman"