Learning a language is not just learning grammar but also learning the correct usage of words. The right word used in the right context, conveys what you want to say quite precisely. On the other hand, wrong usage can be confusing. English language has experienced an explosive proliferation of words over the last century. As it attained the status of an international language, many words from regional languages got assimilated and there was an added influx of slang from different regions, as well as jargon from various evolving fields. The purpose of language is to exactly convey ideas, thoughts, and emotions. An ideal language would have economy of words and a compact grammar, with ideally a word for everything. However, there is a lot of redundancy or superfluousness, when it comes to words as there is more than one word to describe one idea. The words may be exactly alike in meaning but each one of them may have become reserved for a specific context due to convention. The case of differences between insure, ensure, and assure is somewhat of that kind. They are not entirely dissimilar in meaning but they are used in different contexts. In the text that follows, I present a definition of all three words and then point out the usage differences. Insure Vs. Ensure. Vs. Assure: What's the Difference? The fact that you can say one thing in more than one ways, choosing more than one word, is testimony to the richness of a language, but it can be confusing for the beginner who is picking up the language. Let me define the three words first. The definitions of all three words are excerpts from the Oxford English Dictionary, which is considered to be the acclaimed authority on the language. Here is a clear distinction between them, with respect to grammar and composition. Semantic Difference The nature of all three words is that of verbs (words that describe some form of action) and here are their Oxford Dictionary definitions.

Word	Meaning
Insure	arrange for compensation in the event of damage to or loss of (property), or injury to or the death of (someone), in exchange for regular payments to a company or to the state secure or protect someone against (a possible contingency) another term for ensure
Ensure	make certain that (something) will occur or be the case make certain of obtaining or providing (something) make sure that (a problem) does not occur
Assure	tell someone something positively to dispel any doubts make (something) certain to happen chiefly British English: cover (a life) by assurance

Usage When do you use insure or ensure or assure? Here are some examples that will make it clear.

Word	Usage Example
Insure	'When you insure your assets, you reduce risk.'
Ensure	'To ensure safety, modern houses are built to withstand earthquakes.'
Assure	'Harry assured Becky that no other person would ever come between them.'

When you come across a new word, take the pains to lookup that word in a dictionary where they discuss usage and also try to remember the context in which it was used. To sum up the differences in a nutshell, insure is used when arranging for financial security of an asset or a person, ensure is used when something needs to be guaranteed, and assure is used in personal conversation when dispelling doubts or promising something. Insure and ensure can otherwise be interchangeably used, while assure is a bit different and used in a largely different context.