Yo Kass answered
One correct translation for the phrase 'You have beautiful eyes' in Italian is hai dei begli occhi but, although the answer to this question might appear to be a fairly simple translation, there are a few variants that make its explanation a little trickier.
Occhi
The word for 'eyes' in Italian is occhi and it takes the masculine grammatical gender in Italian. This means that any associated words will have a masculine inflection, in accordance with the gender of the noun.
Gender Agreement
The word bello, the Italian adjective equivalent of 'beautiful', is one of the words that must show agreement with the noun occhi in the above phrase.
Depending on where the word bello appears in a sentence, it will take on a different form.
For example, the masculine plural form (which the word occhi appears as here) can be: belli (at the end of a sentence or alone), bei (before a consonant) begli' (before a vowel) and also begli (before gn, pn, ps, x, c and 'impure s').
The form that we're interested in is begli because the word occhio begins with a vowel.
Partitive Articles
The partitive article in Italian is expressed by the preposition di combined with the appropriate definite article (le, lo, la, l', gli etc..). These articles are also influenced by the gender and number of the related noun, with the masculine plural dei appropriate before a consonant.
Variations
The most common variation of the phrase hai dei begli occhi is hai dei bei occhi. The main reason for the use of bei instead of begli, to my knowledge, is to make the phrase flow in a more natural way. This could be described as a case of syncope in linguistics, where a medial sound is dropped to encourage the flow of a sentence (although this is complicated by the dropping of a noun sounding exactly like a different form of the article).
Another way around this problem would be to restructure the sentence to something like hai degli occhi belli where dei changes to degli because it proceeds a noun, and begli thakes the belli form because it comes at the end of the sentence.
Occhi
The word for 'eyes' in Italian is occhi and it takes the masculine grammatical gender in Italian. This means that any associated words will have a masculine inflection, in accordance with the gender of the noun.
Gender Agreement
The word bello, the Italian adjective equivalent of 'beautiful', is one of the words that must show agreement with the noun occhi in the above phrase.
Depending on where the word bello appears in a sentence, it will take on a different form.
For example, the masculine plural form (which the word occhi appears as here) can be: belli (at the end of a sentence or alone), bei (before a consonant) begli' (before a vowel) and also begli (before gn, pn, ps, x, c and 'impure s').
The form that we're interested in is begli because the word occhio begins with a vowel.
Partitive Articles
The partitive article in Italian is expressed by the preposition di combined with the appropriate definite article (le, lo, la, l', gli etc..). These articles are also influenced by the gender and number of the related noun, with the masculine plural dei appropriate before a consonant.
Variations
The most common variation of the phrase hai dei begli occhi is hai dei bei occhi. The main reason for the use of bei instead of begli, to my knowledge, is to make the phrase flow in a more natural way. This could be described as a case of syncope in linguistics, where a medial sound is dropped to encourage the flow of a sentence (although this is complicated by the dropping of a noun sounding exactly like a different form of the article).
Another way around this problem would be to restructure the sentence to something like hai degli occhi belli where dei changes to degli because it proceeds a noun, and begli thakes the belli form because it comes at the end of the sentence.