Learn Arabic (Modern Standard): اشترت الطباخة نحو خمسين كيلو من اللحم. - The cook bought about fifty kilos of meat.

In this sentence, نحو acts as the direct object of the verb اشترت (bought). Because it functions as a noun meaning 'an amount of' or 'approximately', it forms an idhafa (possessive structure) with the number that immediately follows it.

Why do we use خمسين (fifty) here instead of خمسون?

The word نحو forces the following word into the genitive case (majrur) because they are locked together in an idhafa. For the 'tens' numbers (20, 30, 40, etc.), the genitive form ends in ـين (-iin), making it خمسين.

Could I use حوالي or تقريباً instead of نحو here?

Yes, but the sentence structure would change slightly. حوالي works just like نحو and goes right before the number. However, تقريباً is an adverb, so it usually goes at the end of the phrase: خمسين كيلو من اللحم تقريباً.

Why is كيلو singular when the English translation says 'kilos'?

In Arabic, any number from 11 to 99 must be followed by a singular noun. Even though 50 requires a plural in English, Arabic grammar requires the singular form كيلو rather than its plural.