If you’ve ever tried learning Modern Hebrew, you may have noticed that it isn’t the same as the Hebrew you learn in Tanach or Chazal. In fact, it’s far from being that Hebrew. The vocabulary is partially made up and borrowed from other languages, the grammar is more limited and in some cases innovative, and the pronunciation is supposed to be kind of like Sefaradi for European Ashkenazim.
It should be noted that Jewish linguists (e.g. Rav Sa’adiah Gaon, Dunash ibn Labrat, Menachem ibn Saruk, Rashi, Radak, Ibn Ezra, and every huge luminary of Torah) have been trying to figure out Lashon HaKodesh since the time of Chazal. It’s also worth remembering that Tanach and Talmud do not contain every word or root or form in Hebrew (if you need, there’s at least a Rashash in Nedarim that says that). It’s also possible that Chazal themselves did not know every possible word, since they too used Greek and Latin sometimes. (Parenthetically, the Rishonim on Tanach sometimes also comment on words that seem to be the same in foreign languages, but that’s no indication of causality.)
Without getting into all of that, though, one thing should be apparent: Hebrew is a language. If you’ve ever learned a language (even English), you know very well that languages are really complicated. Even if you speak English fluently, you probably aren’t an expert on it, and you probably realize that every time you take a standardized test. Language is also an art. Rambam mentions that we needed a template for davening to be instituted by the Anshei K’nesses Ha’Gedolah because exile brought other languages into the Jewish mind, thus crippling our ability to articulate. In Chovos HaLevavos, Rabbeinu Bachya ibn Paquda lists ten levels of Torah study; you’d be surprised at how many are linguistic.
To take it a step deeper, it is a fundamental of Torah that Hebrew is the Unique Language. It is the DNA of existence: the simplified, symbolic expression of the unfathomable. With this special language, the universe comes into being and with it the Mikdash is designed. The Torah, as the Hitchhiker’s Guide to Reality, is quite understandably encoded with this DNA. It is through the channels of this language that a prophet elevates his consciousness and takes the world in his coat-tails (and we do the same in our use of it, whether we know it or not). Angels only know Hebrew, and there is literally a word for everything in its essence.
The language of our people is wonderful, rich, and divinely designed. It is calculated and endless. Its relatively small alphabet and contained grammar are only greater indications of its density and its meaning (“Rabi Akiva would sit and derive hills of halachos from each [letter’s] ‘crown’”). We have such an infinitesimal grasp of our language; one day we will be proud of it, we will live it, and we will use it to create worlds.