Στο μικρό κλαδί είδα σήμερα δύο καινούρια φύλλα.

Στο is the contracted form of σε το.

In Modern Greek, σε + the definite article often combines into one word:

• σε + το = στο
• σε + τη(ν) = στη(ν)
• σε + τον = στον

So στο μικρό κλαδί is literally on/in/at the small branch, depending on context.

Greek σε is broader than any one English preposition. It can mean in, on, at, or to, depending on the situation.

So:

• στο σπίτι = in the house / at home
• στο τραπέζι = on the table
• στο σχολείο = at school / to school in some contexts

In this sentence, the meaning is location, so English uses on.

Because κλαδί is a neuter singular noun, and μικρό has to agree with it.

So:

• κλαδί = neuter singular
• μικρό = neuter singular form of μικρός

Also, σε normally takes the accusative in Modern Greek. But with neuter nouns, the nominative and accusative are often identical, so the form looks unchanged:

• nominative: το μικρό κλαδί
• accusative: το μικρό κλαδί

That is why you see στο μικρό κλαδί.

Είδα is the aorist form, which is the normal simple past in Greek for a completed event.

Here it means something like I saw as a single completed action.

Compare:

• βλέπω = I see / I am seeing
• είδα = I saw
• έβλεπα = I was seeing / used to see

In this sentence, είδα fits because the speaker is talking about one completed observation.

Yes. Βλέπω and είδα belong together, even though the forms are irregular.

This is a very common verb pair:

• present: βλέπω = I see
• aorist: είδα = I saw

So this is something you mostly just have to learn as an irregular pattern.

Yes, it could move. Greek word order is more flexible than English word order.

This sentence puts the pieces in this order:

• Στο μικρό κλαδί = location/topic first
• είδα = verb
• σήμερα = time
• δύο καινούρια φύλλα = object

But other orders are also possible, for example:

• Σήμερα είδα δύο καινούρια φύλλα στο μικρό κλαδί.
• Είδα σήμερα δύο καινούρια φύλλα στο μικρό κλαδί.

The meaning stays basically the same, but the emphasis changes slightly.

In Modern Greek, δύο is generally indeclinable, which means it does not change form for gender or case.

So you use δύο with masculine, feminine, and neuter nouns:

• δύο άντρες
• δύο γυναίκες
• δύο φύλλα

The noun and adjective show the necessary gender/number information, not the numeral.

Because καινούρια agrees with φύλλα, which is neuter plural.

The adjective καινούριος has these forms:

• masculine singular: καινούριος
• feminine singular: καινούρια
• neuter singular: καινούριο
• neuter plural: καινούρια

So:

• καινούριο φύλλο = new leaf
• καινούρια φύλλα = new leaves

A detail that often confuses learners: the neuter plural form καινούρια looks the same as the feminine singular form, but here it is clearly neuter plural because it goes with φύλλα.

The dictionary form is φύλλο, meaning leaf.

Its plural is:

• singular: το φύλλο
• plural: τα φύλλα

So φύλλα here means leaves.

Here φύλλα is in the accusative plural because it is the direct object of είδα.

However, with many neuter nouns in Greek, the nominative and accusative are identical:

• nominative plural: τα φύλλα
• accusative plural: τα φύλλα

So even though it is the object, the form does not change.

Because Greek often leaves plural nouns without an article when they are indefinite.

English can say two new leaves, and Greek does the same:

• δύο καινούρια φύλλα

Greek does not really have a normal plural equivalent of a/an, so bare plurals are very common.

If you added the article, τα δύο καινούρια φύλλα, it would usually mean the two new leaves, referring to specific ones already known in the conversation.

Yes, you could.

• καινούρια φύλλα = new leaves
• νέα φύλλα = also new leaves

In many contexts, they are interchangeable. But καινούριος often stresses brand-new or newly appeared a bit more clearly, while νέος can also mean young, new, or recent, depending on context.

So in this sentence, καινούρια is a very natural choice.