Μετά την τελεία, γράφουμε το πρώτο γράμμα με κεφαλαίο.

Here τελεία means the punctuation mark period / full stop.

A few useful notes:

• Literally, τελεία can also mean dot.
• In grammar/punctuation talk, η τελεία = the full stop / period.
• So Μετά την τελεία means after the period/full stop.

Because μετά is a preposition here, and in Modern Greek it is followed by the accusative case.

So:

• η τελεία = nominative, the period
• την τελεία = accusative, the period after a preposition like μετά

Compare:

• Η τελεία είναι εδώ. = The period is here.
• Μετά την τελεία... = After the period...

When μετά is used as a preposition meaning after, yes, in Modern Greek it normally takes the accusative:

• μετά το μάθημα = after the lesson
• μετά τη δουλειά = after work
• μετά την τελεία = after the period

You may also see μετά used more loosely as an adverb meaning later / afterwards, where no noun follows:

• Θα το κάνω μετά. = I’ll do it later.

Not necessarily. Greek often uses first person plural in explanations, instructions, and general rules, just like English can say we in a general sense.

So γράφουμε here means something like:

• we write
• we use
• one writes
• you write in a general instructional sense

It is a natural way to state a writing rule:

• Μετά την τελεία, γράφουμε... = After a period, we write...

It does not have to mean a specific group of people.

Because γράμμα is a neuter noun, and both the article and adjective must agree with it.

So:

• το = neuter singular the
• πρώτο = neuter singular first
• γράμμα = letter

That gives:

• το πρώτο γράμμα = the first letter

This is standard Greek agreement:

• article + adjective + noun all match in gender, number, and case

Yes. Here γράμμα means a letter of the alphabet.

Greek uses γράμμα for an alphabet letter, for example:

• το γράμμα Α = the letter A

The same word can also mean letter in the sense of written message, depending on context, but in this sentence the meaning is clearly alphabet letter because it talks about capitalization.

It means with a capital letter or capitalized.

So:

• γράφουμε το πρώτο γράμμα με κεφαλαίο = we write the first letter with a capital letter

Why κεφαλαίο?

• κεφαλαίο is the neuter singular form, matching the idea of γράμμα
• you can think of it as short for με κεφαλαίο γράμμα

In other words, the sentence is saying that the first letter should be capital.

A useful contrast:

• με κεφαλαίο = with a capital initial letter
• με κεφαλαία γράμματα = in capital letters / all caps

Because Μετά την τελεία is an introductory phrase, and Greek often separates that kind of phrase with a comma.

So the comma helps mark the structure:

• Μετά την τελεία, = introductory time/order phrase
• γράφουμε το πρώτο γράμμα με κεφαλαίο. = main statement

In many cases, especially in shorter sentences, you may also see this written without a comma:

• Μετά την τελεία γράφουμε το πρώτο γράμμα με κεφαλαίο.

Both are understandable; the comma mainly adds clarity and a slight pause.

Yes. Greek word order is more flexible than English word order.

This sentence begins with Μετά την τελεία to emphasize the condition or situation first:

• After the period, ...

That is very natural in a rule or instruction.

You could rearrange parts of the sentence, but the emphasis would change. For example:

• Γράφουμε το πρώτο γράμμα με κεφαλαίο μετά την τελεία.

This is still understandable, but it sounds less natural for a general rule because μετά την τελεία comes later. The original order is the most straightforward for teaching a writing rule.