Is the statement "Jennifer is on the front row." grammatically correct? I was told that this statement is incorrect because Jennifer cannot get on top of the row but she can get in the row. Please clarify which is correct to use in the sample sentence above.
If you are giving Jennifer's location in an audience, she is in the front row, in the basic sense of in referring to a position within something. She may be standing in the row, and in it because she is occupying the space within the seats and those seats in front; she may be sitting in the row, and in it because the seat is somewhere in the sequence of seats in the row.
When referring to position or location, on usually indicates resting on an outer or upper surface, or proximity to a point on a line or border, neither of which is applicable to a front row of seats. But on would be applicable in a number of other narrow scenarios, as it has many uses other than the primary location-related meanings.
For example, on can be a function word to indicate the focus of obligation or responsibility (Merriam-Webster definition 7c). Perhaps one is describing work assignments:
The security staff take these positions during intermission: Jan and Rick are on toilet lines, Christina is on fire exits, Oscar is on cashbox, and Jennifer is on the front row.
Another use is to indicate destination or the focus of some action, movement, or directed effort (MW 9a). Perhaps one is going through an auditorium sequentially:
In advance of the speech, bomb squads are sweeping the house. The mezzanine is completed, and in the loge, Thomas is on row 23, but in the orchestra, Jennifer is on the front row still.
It depends on how you think of the row
The answer depends on how you are thinking of the row, as mentioned by Araucaria above.
What is a row? If it is a row of people, you are within the row, you are part of the row, you are thus 'in' the row - e.g. I will be sitting in the 4th row. If you said 'on' when talking about the row of people, it would suggest you are on top of the people.
If however, you are talking about the actual row of seats, and thinking of the row as a collective single object, then you could in fact be 'on' the row - e.g. I will be sitting on the 4th row.
In my own personal experience, 'in' is used most often in this context. I have never heard someone say they are 'on' a row in the context of a row at a concert or venue.
In response to Edwin Ashworth's claim that Google gives him such a high result when searching for 'on the front row'; a similar search using 'in the front row' will give roughly if not exactly the same amount of results. You have to understand google's method for fetching up results, and based on the two searches giving the same result I'd assume Google is disregarding the 'in' or 'on' preposition as it doesn't help filter the result enough - i.e. it doesn't distinguish it enough, so this can't be used as evidence for or against.
One of the answers above mentioned an example as such 'I am on oxford street' - this is correct because you are standing on the street, you are on top of it.
Also mentioned was 'I am on the metropolitan line' (an underground subway route in England) - to avoid confusion, the reason why 'on' works in this sentence is because he says he is 'on the line' which is to mean, he is 'in' the carriage, but the carriage is 'on' the line, so he is effectively 'on' the line,
There are also figures of speech to contend with. For example, when on the phone to a friend in London and someone asks you what you are doing, you say 'I am on the line to London', which is not literal but metaphorical. However, one should be able to assume the differences as they're often obviously improbable -i.e. you wouldn't be on top of the phone line (unless you're a tightrope walker).
This is fine (sometimes).
We are interpreting it as:
"Jennifer is on a seat in the front row"
and we just don't mention the seat because it isn't needed - what else would she sit on?
If, however, you mean:
"Jennifer is in the front row of a dance"
it is in. On is only for when you are sitting on the front row of a theatre / lecture / cinema.