【Think】 ,  【conceive】 ,  【imagine】 ,  【fancy】 ,  【realize】 ,  【envisage】 ,  【envision】  are comparable when they mean to form an idea or notion of something in the mind.

【Think】 , the most general and least explicit word of this group, may imply nothing more than the entrance of an idea or notion into one's mind, but often it suggests some consideration or reflection typically resulting in a decision or judgment or it implies a conscious mental act such as a recalling or recollection or a bringing of a definite picture or a clear idea into one's mind or the framing of a purpose or intention.

【Conceive】 implies a bringing forth in the mind of an organized product of thought (as an idea, a plan, a project, or a design); often the term suggests the growth and development of that idea as the mind dwells upon it and brings it into being.

【Imagine】  carries a stronger implication than  【conceive】  does of visualization or of definitely creating a mental image of a thing; thus, one can  【conceive】  , but scarcely  【imagine】 , a world of more than three dimensions.

【Fancy】  (see also LIKE ) may differ little from  【imagine】 , but it commonly suggests unreality or a degree of untruth in the idea conceived or the image developed; sometimes it even implies a tendency to cut oneself off from facts and to be governed by one's dreams or desires.

【Realize】  (see also  【REALIZE】 1 ) implies a very vivid conception or imagination through which a grasp of the significance of a thing is attained.

【Envisage】  and  【envision】 imply a conception or imagination actually or potentially so clear or so detailed that one does or can contemplate it as though it were before one.