The skill teaches mostly syllables/sounds of the letters, plus some nouns, all neuter gender with the definite article το (the, neuter singular form). Most of them are similar to their English translation except το νερό (the water). The one-syllable words ναι (yes) and και (and) are introduced, and the first adjective: ροζ (pink). Adjectives preceed the nouns in Greek, as in English. We form our first sentences using είναι ([it] is), and we learn that nouns can be used without indefinite article: Είναι καρότο (It is a carrot).
The letter sigma has two forms in lower case: σ at the beginning or in the middle of a word, and ς at the end. Apart from this, there are more syllables/sounds, the preposition με (with), the transitive verb κάνει ([he/she/it] makes), and the emphasized subject pronoun αυτός (he). As an object of κάνει, neuter nouns do not change, they remain the same as in subject position. The preposition στο (in/at) is introduced to describe locations. It already has the article included. One may wonder how "at a museum" instead of "at the museum" would be expressed, but this is not taught yet. Newly introduced nouns still all have neuter gender.
The definite article (the) for masuline nouns in singular is ο, and for feminine nouns it is η: Ο άντρας και η γυναίκα (The man and the woman). Names are used with article when talking about someone (but not when addressing a person). "Someone is a + profession" does not use the indefinite article in Greek (as in Spanish or German), and a female's profession may be given in masculine form: Η Μαρία είναι αρχιτέκτονας. Γεια σου (hi/hello) is used to greet someone informally.
More nouns of all genders are introduced, masculine, feminine and neuter. As before, most of them are similar to English words. "Spaghetti" is taught in singular, which would refer to a single piece of spaghetti. There is a new adjective, too: μεγάλο (big). For now it is solely used with neuter nouns.
The verb form είναι is the same in 3rd person singular and plural: Το νερό και ο καφές είναι ροζ (The water and the coffee are pink). Also, ροζ obviously does not change with gender or number.
We are getting to know indefinite articles now: ένας goes with masculine nouns, μία is for feminine gender, and ένα for neuter. Then there is the demonstrative pronoun/article "this": αυτός (masculine), αυτή (feminine) and αυτό (neuter). These can be used on their own, as in "This is ...", but when used in front of a noun, we need the definitive article in addition. We have had αυτός before where it meant "he", e.g. in αυτός κάνει ρύζι ("he makes rice"). "This" would not make sense there (but "this one" would be another option to translate it). In sentences like αυτός είναι άντρας both "this is a man" or "he is a man" might be possible translations (and there is hardly any difference in meaning). There also is a new conjugation of "to be": εγώ είμαι or only είμαι means "I am". Both the subject pronoun εγώ and the indefinite articles are optional in Greek, there are examples with and without them.
The verbs for "to eat" an "to drink" are used in 1st (τρώω, πίνω) and 3rd person singular (τρώει, πίνει) with different neuter objects.
This skill teaches the plural forms of nouns, and verbs in different conjugations. Not all conjugations are covered yet, but we can observe some patterns:
So, "to eat", τρώω, seems to behave a little special, possibly because the stem ends in ω? Additionally, the stem of τρώω only is one syllable, unlike other verbs taught in this skill.
A collection of useful sayings to get to know someone. It includes what I interpret as a dialog which uses the plural you form in the question, but "I" instead of "we" in the answer: Μιλάτε ελληνικά; - Ναι, μιλάω ελληνικά. This seems to be the courtesy form ("formal you"), which coincides with plural you in Greek (same as in French). "What's your name? My name is ..." is interesting. My first guess was that it is reflexive (as in Spanish), but the verb λένε doesn't change with the person, and looking into what we learned about verb conjugation in the last skill, the most similar one is τρώνε, so the literal translation must be more like "How do they call you? They call me ..."
Names of locations (countries, regions, cities) in this skill are feminine, and the preposition στο we learned earlier for in/at changes to στην in front of them. There is another one indicating origin ("from"), which is από την with the feminine nouns used in this lesson.
Δεν (not) has a variation, too: it may become Δε when followed by a "continuant" consonant like μ. Continuant means you can keep making this sound for a longer time (μμμμμ), while "non-continuant" can only be repeated (.
Conjugations of the verb "to speak", μιλάω, in this skill:
This is fairly close to τρώω, and both stems end in a vocal. Filling the gaps by guessing would get us εσείς τρώτε for "you [all] eat", εμείς μιλάμε for "we speak", and αυτοί μιλάνε. Taking a look a a conjugation table, these seem correct, but it may be worth noting that there are some additional forms for verbs with a stem ending in α, which will be covered in detail in the tips of skill 2.07 Present 1.
When used together with a noun (my ...), possessive adjectives can have two different forms as explained in the tips: after definite article and noun as in ο καφές μου, or - more emphatic - ο δικός μου καφές. The latter is usually translated to "my own ..." on Dulingo to reflect the emphasis.
When used standalone as a pronoun (... is mine), possessive pronouns have to take the latter two-part form, so it would be ο καφές είναι δικός μου without having special emphasis.
With an additional adjective, μου, σου etc. can be placed between adjective and noun: το μικρό μας παιδί. Other options as per solution list: after the noun (το μικρό παιδί μας) or after the noun, but with repitition of the definite article: το μικρό το παιδί μας, or with the adjective last, with duplicate article, too: το παιδί μας το μικρό.
The sentences use verbs that are already known: to eat, to drink, to have.
We get to know a lot more nouns of all three genders. Compound nouns like apple juice and orange juice are built by using the two nouns, but in inversed order compared to English: ο χυμός μήλο, ο χυμός πορτοκάλι (dictionaries also have ο χυμός μήλου, so obviously there is an alternative way to say apple juice).
The adjective νόστιμο we learned earlier changes when it is used with masculine and feminine noun: Ο χυμός μήλο είναι πολύ νόστιμος and Η πίτσα είναι νόστιμη. An adjective in neuter plural form is present as well: Τα κεράσια είναι φρέσκα.
Another set of nouns. Interestingly, there is a neuter plural form for some words and a different one for a female individual: τα αδέλφια (the siblings), η αδερφή (the sister). Brother isn't taught yet, not sisters or brothers in plural. Very similar are the words for cousins: τα ξαδέρφια and (female) cousin: η ξαδέρφη, but the accent does not move to the last sillable for the female noun. After asking in the duome forum, I also got to know that all these words can be spelled and pronounced either with λ or with ρ.
Duolingo doesn't have tips on this skill.
Even more nouns. I struggled with η κότα as opposed to το κοτόπουλο. Κότα is the animal and κοτόπουλο is either the young animal or the meat. While you can use κότα metaphorically in the sense of cowardice (Είσαι κότα; - "Are you a chicken/coward?"), κοτόπουλο only has the literal meaning.
The usage of το κατοικίδιο was not so easy to me either. It is used before the animal if the species is mentioned (same as in English): ένα κατοικίδιο ποντίκι - a pet mouse, and can be used referring to people on its own: Είμαι το κατοικίδιό σου; - Am I your pet?, but it seems common to add ζώο if you are talking about animals without specifying which kind: Έχω ένα κατοικίδιο ζώο. - I have a pet. I can't tell if ζώο can be dropped.
We have learned almost 100 nouns so far, and taking a look at them very common endings are -ας and -ος for for masculine nouns, -α and -η for feminine ones and -ο and -ι for neuter gender. We also had plurals for some of them in previous lessons, namely
This lesson adds the plural for neuter nouns ending in -ο: το άλογο - τα άλογα