"A mom is talking to a child."
Translation:Мама говорит с ребёнком.
Russian is typically SVO language: subject-verb-object, so usually you should prefer the same ordering as English has. However, Russian has cases and prepositions to allow free ordering, and in some cases your sentence might be okay (and it will always be 100% understood). Especially it is true for the spoken language: human beings have erratic minds, chaotic thoughts, easily jumping from an object to a subject etc.
I am a native speaker. The sentence is not wrong. The meaning may vary a lot, though, depending on the intonation. If you stress мама, it may mean “it’s the mom who is talking to the child” or “a mom is talking to a child” (the latter is more commonly expressed as “Какая-то мамаша с ребёнком разговаривает». If you stress «с ребёнком», it may mean “my/the mom is talking to a child” or “it is the child who my mom is talking to”, depending on the situation. Finally, if you stress «говорит», the sentence will be understood as “The mom does speak with the child” (i.e. they are on speaking terms)
If you say мама without a possesive adjective (e.g. твоя мама, его мама) it usually implies that you are talking about your own mother. When it is a mom of a child we use the word мамаша which, if applied to a mom we know, will not be very polite. But it would be the most natural equivalent of a mom who is a stranger and whose child is a stranger. So my answer (as a native speaker) is Мамаша говорит/разговаривает с ребенком.
Одна мать is only used for contrast: Во дворе две женщины с детьми. Одна мать говорит с ребенком, а другая молчит. It's OK to translate "a mom" as мама too, but it may sound ambiguous unless it is obvious who you're referring to. Мать in this context will correspond to 'a mother/the mother'. Какая-то женщина разговаривает со своим ребенком (A woman is talking to her child) is also an option.
Thank you for the reply. The Duolingo sentence reminded of prior advice: A Russian teacher once said if talking about a particular person, a man told me... if one says, человек сказал мне, a Russian would be confused and ask, "What person?" So it would be better so say "один человек сказал мне" A person said to me.
That's right. However, the rule applicable to a generic word (человек) cannot be applied to a term of kinship (мать). On the one hand, the subject мать usually refers to the speaker's mother, on the other hand, we tend to relate it the object of the verb. Thus, out of context, мать сказала ему can be interpreted as "my mother said to him" and as "his mother said him". About a century ago the same was true about the words мамаша and папаша which, in those days, low-class people often used to refer to their own parents. Nowadays they are mostly used as "a mom" / "a dad" to demonstrate that they have no relation to the speaker or to show disapproval of their behavior (e.g. его мамаша means "his mother, a woman whose behavior I don't approve of").