In answer to the tough question about the most appropriate use of "only" in a grammatically, syntactically and semantically correct sentence, I'll try to concentrate more on how the placement of only in the sentence is meaning controlling. In other words, the use of only as a modifier of a word should be placed directly before the word or clause to be modified.
"Only" is so disturbing as a modifier because its placement in the utterance counts much to the meaning you want to convey. Be it an "adjective" or an "adverb", the word "Only" could affect the meaning of what you want to say if you don't carefully use it in your statement. As an adjective, "only" is almost controllable; but all the trouble which comes from "only" is only when it is used as an adverb . "This is my only child": this implies that I have no other children and "only" here is used as an adjective. Thus, there is no problem at all. Still which is correct then: Is it, "IT'S ONLY ME!" or is it, "IT'S ONLY I!"? According to grammarians, it is the second. But most people use the first on the basis that, "A mistaken sentence that makes me understood is better that a correct sentence that makes a jerk of me"; what a mess!
Though we feel it is final, definite or even exaggerated when "only" precedes the subject intending to modify it, this means that we want our listener or reader to understand that the subject be it (Susan, you, Peter or my mother as in the examples above) could do the deeds (actions) attributed to them but nobody else.
When "only" precedes the verb, this implies that the listener or reader is meant to understand that the subject be it (She, we, They or Johnny as in the examples above) did but only the deeds (actions) stated in the sentences.
When "only" follows the verb, this means that you cannot ask the subject to do something else except the one or ones mentioned after "only". That's to say that you cannot ask Leila to play another game as she plays only but tennis. As well, you wouldn't invite the guests to share your barbecue because they are vegetarians and so on.
When "only" is final, the meaning depends on many other factors such as intonation, tone and emphasis. We previously mentioned the sentence, "It's my only child" and we said that "only" is used here as an adjective and it implicates that the speaker has only but that "unique" son. Now, someone did a blunder and someone else came and said, "It’s a boy only!" He projected to state that it is not harmful as the go-getter is only but someone not to be taken critically. Despite the fact that it seems a far fetched way of saying it, this utterance is likely to be most expressed by non-native speakers.
"The club is for old people only". There is exception here. Nobody is allowed in the club except for old people. Only old people are admissible. "Only" here modifies the word before it, notably "old people".
Generally speaking some of the examples above are far fetched and sometimes overstated. Any slight misplacement of "only" would prompt a disaster as far as meaning is concerned; therefore you should always try to avoid using most of them if you are not sure. There are other ways to say the same thing without too much care for preventing any possible misunderstanding a sentence with 'only' would bring about. I advise you to push 'only' towards modifying the exact word in the sentence as a safe way to make your message clear and void of any ambiguity possible. Be careful as to what word ‘only’ is used to modify. See what I mean. Can you say which of the following utterances conveys the meaning intended properly?!
- I only will come if you invite me.
- I will come only if you invite me.
- I am only interested in English grammar.
- I am interested in English grammar only.
This is on one hand; on the other hand you can in some cases replace 'only' with 'just':
Finally, in order for you to be comprehensible and for your message to be ambiguity-free, please do avoid the misplacement of "only" in your utterances!
- I saw her only yesterday.
- I saw her just yesterday.
- Ali only put the book on the table in silence and left.
- Ali just put the book on the table in silence and left.