Ο καφές είναι λίγος.

In Greek, a singular countable noun used as the subject almost always takes a definite article.

• Ο καφές = the coffee (in general / the coffee we’re talking about)
• Greek normally does not say just Καφές είναι λίγος. That sounds wrong or very odd.
• Even when English uses a more abstract or impersonal structure (There is little coffee), Greek often prefers a normal subject:
  Ο καφές είναι λίγος = literally The coffee is little (in quantity) → idiomatically There is little coffee / The coffee is not much.

So the article Ο is required here because καφές is the subject of the sentence.

Καφές is masculine.

• The definite article ο marks masculine singular: ο καφές.
• Many masculine nouns in Greek end in -ής or -ές in the nominative singular:
  ο καφές, ο μαθητής (the student), ο τουριστής (the tourist).
• You usually learn the gender together with the noun plus its article: ο καφές (m), η ζάχαρη (f), το γάλα (n).

So you should memorize ο καφές (masculine) as a whole phrase.

Because λίγος is functioning as an adjective that must agree with ο καφές in gender, number, and case.

• ο καφές → masculine, singular, nominative
• The matching form of the adjective is: λίγος (masc. nom. sg.)

Basic forms of λίγος (little, few):

• Masculine: λίγος (sg.), λίγοι (pl.)
• Feminine: λίγη (sg.), λίγες (pl.)
• Neuter: λίγο (sg.), λίγα (pl.)

So:

• Ο καφές είναι λίγος. – The coffee (amount) is little.
• Η ζάχαρη είναι λίγη. – The sugar is little.
• Το γάλα είναι λίγο. – The milk is little.

Here we need λίγος to match ο καφές.

There are two main uses:

1. Adjective (agrees with a noun in gender/number/case)

   • Masculine: λίγος καφές – a little coffee
   • Feminine: λίγη ζάχαρη – a little sugar
   • Neuter: λίγο γάλα – a little milk
   • In Ο καφές είναι λίγος, λίγος is an adjective describing the noun καφές.

2. Adverb / neuter form (often used as “a little / a bit”)

   • Θέλω λίγο καφέ. – I want a little coffee.
     (Here λίγο is neuter, used in a quantity expression in front of the noun.)
   • Πεινάω λίγο. – I am a little hungry.
   • Είναι λίγο ακριβό. – It is a bit expensive.

If you say Ο καφές είναι λίγο without anything after it, it sounds incomplete. You’d expect:
Ο καφές είναι λίγο κρύος. – The coffee is a bit cold.
There λίγο is an adverb modifying κρύος.

It talks about quantity, not quality.

• Ο καφές είναι λίγος. = The amount of coffee is small / There is not much coffee.
• If you want to complain about quality, you would use other adjectives:
  
  • Ο καφές είναι κακός. – The coffee is bad.
  • Ο καφές είναι αδύναμος. – The coffee is weak.
  • Ο καφές είναι κρύος. – The coffee is cold.

So λίγος here means little (not enough) in terms of amount.

It usually has a slight negative or complaining tone: the quantity is small and probably not enough.

• Context where someone is worried:
  Ο καφές είναι λίγος, δεν θα μας φτάσει. – The coffee is little, it won’t be enough for us.
• If you just want to say there is a little coffee in a more neutral way, you might say:
  Έχουμε λίγο καφέ. – We have a little coffee.
  Υπάρχει λίγος καφές. – There is a little coffee.

So είναι λίγος often implies insufficient.

Yes, and the meaning is very close, though the structure is different:

• Ο καφές είναι λίγος.
  Literal: The coffee is little.
  Focus: The coffee (as a specific thing we’re talking about) is not much.

• Υπάρχει λίγος καφές.
  Literal: There exists a little coffee.
  Focus: Simply stating that some amount of coffee exists.

In many contexts they can be interchangeable, but:

• To complain that the amount is not enough, Ο καφές είναι λίγος feels more natural.
• To neutrally report availability, Υπάρχει λίγος καφές is very natural.

No. In standard Greek you need the verb είναι (is) in this sentence.

• Ο καφές είναι λίγος. – correct
• Ο καφές λίγος. – sounds incomplete or like telegraphic speech.

Greek does not usually drop the verb to be in simple present statements like this, unlike some informal patterns in other languages.

Yes, both are grammatically correct, but they change the emphasis.

• Ο καφές είναι λίγος. – neutral word order, normal statement.
• Είναι λίγος ο καφές. – emphasizes λίγος a bit more; often used to stress the result or conclusion.
• Λίγος είναι ο καφές. – strong emphasis on λίγος; often used in contrast, e.g.:
  Λίγος είναι ο καφές και πολλοί είμαστε. – The coffee is little and we are many.

All three are possible, but the original one is the default.

You change both the noun and the adjective to plural:

• Singular: Ο καφές είναι λίγος. – The coffee is little (there isn’t much coffee).
• Plural: Οι καφέδες είναι λίγοι. – The coffees are few / There are few coffees.

Note the changes:

• ο καφές → οι καφέδες (masculine plural, nominative)
• λίγος → λίγοι (masculine plural, nominative)

Both can be translated as little or small, but they focus on different things:

• λίγος = small amount or number (quantity)

  • Ο καφές είναι λίγος. – There is little coffee (not enough amount).
  • Οι καφέδες είναι λίγοι. – There are few coffees.

• μικρός = small size or age

  • Ένα μικρό φλιτζάνι καφέ. – A small cup of coffee.
  • Ένα μικρό παιδί. – A small/young child.

So, Ο καφές είναι μικρός would be strange; you would normally talk about a small cup, not small coffee. For amount, use λίγος.

• καφές: [kaˈfɛs]

  • Stress on the second syllable: καφές.
  • The φ is like f in coffee.

• λίγος: [ˈliɣos]

  • Stress on the first syllable: λίγος.
  • The γ before ο is a voiced velar fricative, similar to a softer gh sound from the back of the throat.
    
    • Between vowels (as in λίγος), it is smoother and more “friction-y” than a hard g.

Putting it together: Ο καφές είναι λίγος → [o kaˈfɛs ˈine ˈliɣos].