Some words are difficult to differentiate. For those with who struggle with how to use “ensure” vs. “assure” vs. “insure,” I offer the following information:
To “assure” a person of something is to make him or her confident of/about it.
According to the Associated Press Stylebook, to “ensure” that something happens is to make certain that it does.
To “insure” is to issue an insurance policy.
How about effect and affect?
Affect and effect are often confused.
According to my favorite dictionary resource (the online — free — version is at http://www.AskOxford.com), “Affect is primarily a verb meaning ‘make a difference to’, as in the changes will affect everyone. Effect is used both as a noun meaning ‘a result’ (e.g. the substance has a pain-killing effect) and as a verb meaning ‘bring about (a result)’, as in she effected a cost-cutting exercise.”
There are, however, some exceptions to this (notably in the field of Psychology). Affect, in psychology, refers to the experience of emotion or feeling.