Autarchy — Autarchy means absolute sovereignty. Autarky (sometimes mis-spelt autarchy) means self-sufficiency. The difference in spelling reflects the different Greek words from which they are derived.
Dependant — In the ordinary usage of today dependant is a noun meaning "a person who depends on another for support, position, etc." (O.E.D.). Dependent is an adjective meaning relying on or subject to something else. Dependants are dependent on the person whose dependants they are.
Enquiry — Enquiry and inquiry have long existed together as alternative spellings of the same word. In America inquiry is dislodging enquiry for all purposes. In England a useful distinction is developing: enquiry is used for asking a question and inquiry for making an investigation. Thus you might enquire what time the inquiry begins.
Forego — To forego is to go before (the foregoing provisions of this Act). To forgo is to go without, to waive (he will forgo his right).
Ise or Ize — On the question whether verbs like organise and nouns like organisation should be spelt with an s or a z the authorities differ. The O.E.D. favours universal ize, arguing that the suffix is always in its origin either Greek or Latin and in both languages it is spelt with a z. So do the University Presses of Oxford and Cambridge. Other authorities, including some English printers, recommend universal ise. Fowler stands between these two opinions. He points out that the O.E.D.'s advice over-simplifies the problem, since there are some verbs (e.g. advertise, comprise, despise, exercise and surmise) which are never spelt ize in this country. On the other hand, he says
"the difficulty of remembering which these ise verbs are is the only reason for making ise universal, and the sacrifice of significance to ease does not seem justified".
This austere conclusion will not commend itself to everyone. It does not do so to the authors of the A.B.C. of English Usage, who say roundly, "the advice given here is to end them all in ise", a verdict with which I respectfully agree.