Why is 'Messiah' interpreted as "a word from Allah" in the Holy Quran?

Question

I read in surah Aali-Imran:45 that Messiah or Jesus is "a word from Him (Allah)." What does "a word from Allah" mean?

إِذْ قَالَتِ الْمَلَائِكَةُ يَا مَرْ‌يَمُ إِنَّ اللَّـهَ يُبَشِّرُ‌كِ بِكَلِمَةٍ مِّنْهُ اسْمُهُ الْمَسِيحُ عِيسَى ابْنُ مَرْ‌يَمَ وَجِيهًا فِي الدُّنْيَا وَالْآخِرَ‌ةِ وَمِنَ الْمُقَرَّ‌بِينَ

When the angels said, 'Mary, God gives thee good tidings of a Word from Him whose name is Messiah, Jesus, son of Mary; high honoured shall he be in this world and the next, near stationed to God.

Answer 1

According to the interpretation of Allameh Muhammad-Hussein Tabatab'ee, 'word' (Arabic: کلمة, kalima) in Quranic application refers to

'that which shows the will of Allah'; it may be an order, e.g., the word of creation when He says to a thing, 'Be'; or it may be a word of revelation and inspiration, etc. (A-Mizan Exegesis)

In this sense, Jesus was described as a "word from Allah" because he was born by Gabriel to the Holy Mary in a miraculous manner without the mediation of common natural causes; a clear manifestation of Allah's creative will.

Answer 2

The interpretation you have brought is a little confusing. Please pay attention to this:

Recall what time the angels said: Maryam! Verily Allah announced unto thee a word from Him: his name Shall be the Masih, Isa, son of Maryam, illustrious in the world and the Hereafter and one of those brought nigh. (45)

Actually the angles brought the name of Messiah from God to Holy Maryam. The angles annunciate Holy Maryam with a son whose name was chosen by Allah.