A vocabulary list is a useful, honest tool, and it is also a flattened one. It gives you a word and a translation, one line each, as if every word behaved the way most English words do: fixed, neutral, usable in any sentence you drop it into. Four features of Greek make that flattening cost more than it does in most languages, and it is worth knowing about them before they surprise you mid-sentence.
1. English is full of Greek roots, and that buys you less than it seems
Photograph, biology, telephone, democracy, chaos, echo, therapy, chronology — an English speaker already carries a sizeable stock of Greek word-parts around without knowing it, in exactly the way English academic vocabulary leans on Latin. That stock is genuinely useful once you reach formal or technical Greek. It does almost nothing for the everyday words you need first, because those are inherited Greek roots that never passed back through English and look nothing like their English descendants: τραπέζι (trapezi, "table") shares nothing visible with "trapeze", though the two are related. Some of the ones that do look related have drifted in meaning rather than transferred cleanly — ιδιώτησ (idiόtis) is simply "private citizen" in Greek, not the insult "idiot" borrowed English made of it.
2. Modern Greek still builds words the way English only borrowed them
English took its Greek vocabulary secondhand, as finished technical terms: "television" is Greek tele welded to Latin vision. Modern Greek, by contrast, keeps building new words out of its own living roots, transparently, so a native speaker can look at a modern coinage and see the parts. Τηλεόραση (tileorasi, "television") is literally "far-seeing". Διαδίκτυο (diadiktyo, "internet") is literally "through-network". Once you notice a handful of these recurring pieces, unfamiliar modern words stop being opaque strings and start being combinations you can half-guess — but only for the words coined this way, which a bare translation column gives you no way to tell apart from the ones that aren't.
3. Three genders, and the case marks the noun itself
Greek nouns are masculine, feminine or neuter, and gender is not just a fact you memorise about the article. Nouns decline across cases — nominative, genitive, accusative, and a vocative for addressing someone directly — and the ending of the noun itself changes, not only the word in front of it. The system is smaller than German's: the modern spoken language has folded the old dative into the genitive and accusative, leaving fewer distinct forms to learn. But where German marks a lot of its case system on the article and leaves many nouns untouched, Greek marks the noun directly. A word list gives you one shape, the nominative singular: ο δρόμοσ (o dromos, "the road"). In an actual sentence, "of the road" is του δρόμου (tou dromou), and "the road" as an object is τον δρόμο (ton dromo). Three different final letters, and it is still one noun.
4. The Greek you half-remember from school is not the Greek you'll hear
Plenty of English speakers meet Greek before ever deciding to learn it: alpha and omega, a bit of mythology, a handful of philosophy terms, perhaps an actual term of Ancient Greek at school. That half-memory is a false friend twice over. The classroom pronunciation usually taught for Ancient Greek predates the very sound mergers covered above, so a letter such as η, taught as a long "e", is pronounced "ee" in the language as it is spoken today. And plenty of vocabulary has moved on even where the ancient word survives in English: the root behind "hippopotamus" is ίπποσ (híppos, "horse"), but the everyday Modern Greek word for horse is άλογο (álogo); ίπποσ survives mainly in formal and compound words, not at the stables. Half-remembered Ancient Greek is a reasonable source of curiosity about where a word came from. It is not a shortcut to the modern spoken vocabulary.
None of the four things above is something a widget can decide for you — they depend on the sentence and the register you're in. What Watch Your Language can do is keep the words themselves in front of you, Greek script with a romanisation alongside, a few at a time on your iPhone Lock Screen and Apple Watch face, so the vocabulary is not the part still slowing you down when you meet these four things for real.
What this means for how you study
None of this argues against building vocabulary early and often. It argues against expecting a word list, on its own, to teach you how to use what is on it. Learn the words. Then meet them again in sentences, where the case ending, the register and the actual modern meaning are decided — that is where a dictionary form turns into a language.
