Good question! Sometimes you can replace one word with another by modifying the sentence while keeping the basic meaning the same. "Propose" and "suggest" are the most interchangeable. (See below) Propose - verb. "I propose we make Ann's birthday party a surprise." Suggest" can be used in place of "propose." Offer - verb or noun. Verb: "I will offer to help him plan Ann's party." For this sentence, you can't substitute, unless you modify the sentence. For example: "I will provide help planning Ann's party." But these two sentences are slightly different in meaning. The first is asking permission. The second sentence is making a statement. Offer as a noun: "I made Ann an offer she couldn't refuse." Suggest - verb. "Can you suggest which present Ann will like?" "Propose" can replace "suggest." (Propose is more assertive than "suggest") Provide - verb. "Can you provide ice cream for Ann's birthday party?" "Provide" specifically refers to giving something, whether it's an object (like ice cream) or an idea. I would consider it the least like the other words. Hope this helps. :-)

There are differences of course, but it all depends on the context and how they are being used. Please keep in mind that they have many different meanings so I am going to give you some examples which are similar but under other circumstances, the meaning might be totally different. Propose and suggest are quite similar; offer and supply might be similar but the difference is more evident. Some examples as verbs: Propose: He proposed an excellent idea. Suggest: She suggested to do it another way. Here the meaning is basically similar although "proposed" might be a bit more direct. Offer: The room offers a nice view. Provide: The meals were provided for them. Here again, the meaning is similar and means "to give". Some examples as a noun: Proposal: His proposal is yet to be accepted. Suggestion: My suggestion was to come back home. Here, the meaning is similar as well; something is being asked, which is basically a proposition. Offer: She thought about an offer of marriage. Providing: Without any providing, the tigers would have probably died. Here the meaning is a proposition for "offer" and a supply for "providing", which means "to give". That might seem to be confusing, but as I said, it all depends on the context and how you want to use them. Does that make sense to you?