• It's or its. Usually an apostrophe indicates ownership, such as in “John’s car”. It also can indicate a contraction, such as “we’re” for “we are”. But, in the case of “it’s” versus “its” all bets are off. “It’s” is used for the contraction “it is” or “it has”; “its” is used to denote the possessive such as in: “The ship suffered a rupture in its hull.”
• Insure, ensure, or assure. Whoa, this is difficult one. You write: “I assure you that I am not the one you want.” Is “assure” correct? Or, if you write: “I will do everything in my power to ensure that you survive the trip.” Or, say you set down: “The company’s policy insures us against falling during the climb.” Well, you get the idea. So, how do you know which is correct? Insure denotes the idea of providing insurance (yeah, the kind those pesky salesmen want you to buy), or the idea of making something sure or certain. Ensure also denotes the idea of making something safe or certain. But, it also implies a virtual guarantee. Think of insure as taking the proper precautions prior to embarking on the risky venture and ensure as providing safety during the venture. Assure means to strongly inform someone of the certainty of a situation. It implies convincing them that something will or will not happen. By the way, each of the above sentence examples involve the proper usage of insure, ensure, and assure.
• Ultimate and penultimate. Penultimate sounds so superior to ultimate that it must mean the greatest, right?. Wrong! Ultimate means the end of a process or the greatest. Penultimate means next to the last. So, saying: “Going to Disney World is the penultimate of vacations,” is wrong (but, I guess that would depend on you being a Disney fan). But, saying: “Friday is the penultimate day of the week,” is correct.
Next time I’ll look at a few more difficult words I struggle with. In the mean time, happy writing.