The question mark is a punctuation mark that is used at the end of a sentence when asking a question. As statements go, that sounds like a no-brainer.
But what is a question? A question is a direct and open request for information, e.g. What time is it? Upon hearing the example sentence, we immediately know it is a question because its first word is an interrogative pronoun. Reading on, we find the inverted verb form word order that indicates a question in English. In this example, the straightforward ‘it is’ has been switched round to ‘is it?’.
Inversion of subject and verb is a feature of Romance languages and English. (Keep in mind that English is not a Romance language like French, Italian, Portuguese, Spanish, and Romanian. English is a West Germanic language, originating from settlers in the 5th century CE. Nevertheless, English does invert its verbs when forming a question.)
Native speakers of other languages, such as Arabic, typically have difficulty with the interrogative inversion. An Arabic speaker whose second language is English might ask, "Why he is doing that?" whereas a native English speaker would ask, "Why is he doing that?" The Arabic speaker would leave it to context and intonation to make clear he was asking a question.
Given the recognisable word order of a question written in English, the question mark at the end of the sentence seems redundant. Unfortunately, though, an emerging form of passive-aggression has hijacked the noble question mark.
Every so often, I receive emails containing statements - not questions - that end with question marks. Often, the offending sentence starts with ‘I thought’, such as ‘I thought we were going to do it my way?’
The sentence is clearly not a question. It is an assertion. The sender asserts that they thought (note the past tense, i.e. they do not think that any more) it was going to be done their way. So, why does the sender use a question mark? I think it is because they have awarded themselves the right to expect an answer, even though they have not asked a question. There is something not quite up-front about that. It’s as though the sender is saying, ‘I’m not going to do you the courtesy of deferring to you by asking an actual question, but I expect an answer nevertheless.’ Perhaps there is more to it. Clearly, the sender is responding to something. It seems they are indicating their surprise at a notification they have received, about a decision to do something in a way they don’t want. If they were to ask a straightforward question, such as ‘Why aren’t we doing this my way?’, they would thus be showing their hand, openly questioning a decision that they do not like. I could then respond by asking them on what grounds are they questioning my decision? By hiding behind the passive-aggressive statement with a question mark, they can perhaps convince themselves they are just sharing a thought, rather than demanding that the decision be reversed. It’s an instruction,without the honesty of a direct imperative. It’s a veiled command to‘Explain yourself.’ Bluntly, you can shove it.