Key Difference: Purpose tries to gauge at the reason behind something that is being done. Purpose defines why the person is doing something he is doing, what is his reasoning behind doing a particular thing and what he plans to achieve from it. The objective is actually a part of a goal. The term objective refers to set tasks or goals that a person wishes to accomplish. Objectives are more concrete and are clearly defined by certain steps that will eventually allow the person to fulfill that particular goal.

The terms purpose and objective are two words that are often used interchangeably as it has subtle differences between them. However, depending on the context in which these words are used can change the meaning of the sentence. Purpose can be used to determine the reason behind a person doing something, while objective refers to something a person wants to accomplish. Also see Aim Vs. Objective

Purpose tries to gauge at the reason behind something that is being done. Purpose defines why the person is doing something he is doing, what is his reasoning behind doing a particular thing and what he plans to achieve from it. For example, Jim’s purpose behind the petition is to stop corruption. As this statement states, Jim is creating a petition but the reason for the petition is to fight corruption. That becomes the purpose of the statement. Another context purpose can be used is to show the determination of doing something. For example the statement, “I have a purpose of seeing my name cleared of any accusation.” This statement shows that the person is determined to see their name cleared, that becomes their commitment. Also see: Goal Vs. Purpose  

Dictionary.com defines ‘purpose’ as:

• The reason for which something exists or is done, made, used, etc.
• An intended or desired result; end; aim; goal.
• Determination; resoluteness.

The objective is actually a part of a goal. The term objective refers to set tasks or goals that a person wishes to accomplish. Objectives are more concrete and are clearly defined by certain steps that will eventually allow the person to fulfill that particular goal. Objectives can be termed as small guidelines that help achieve the goal at hand. They can also be used for motivation purposes. Objectives are often short term and have a limited amount of time frame. They have three parts to it: what the person wants to do, the time frame required and the resources he plans to use. These three things can be answered in an objective. Objectives are also much easier to measure than goals. It asks only if the person finished what he wanted to in the amount of time he had set aside. Objectives can be considered as being more realistic. Also see the difference between goal and ambition. 

Dictionary.com defines ‘objectives’ as:

• Something that one's efforts or actions are intended to attain or accomplish; purpose; goal; target.

Purpose and objective are often used to refer to something that a person wishes to fulfill or something that he intends to achieve/accomplish. However, these are not set to these definitions. The term purpose can also be used to determine why the person is doing something that he is doing. While objective refers to small, tiny guidelines that a person sets to help complete the goal and achieve success. Also see Vision Vs. Goal. 

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