I guess formal and informal refer to two types of essay - you can write a formal essay where you avoid conversational language and such and where you need to be very professional, or you can write informally where you don't have to think about such things, it is very casual.
Technical<span> skills or </span>technical language<span> refers to the skills or terminologies that are typically best understood by people who specialize in that field or area.
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Answer: the infinitive form of the verb of salvation is 'to save'.
What do you mean by that?
if you could explain more clearly i'd be glad to help you out