Το κουμπί στο πουκάμισό μου δεν είναι καλά ραμμένο.

Because κουμπί is a neuter noun in Greek, so it takes the neuter article το.

• το κουμπί = the button
• singular neuter nouns often use το

This also affects other words that agree with it later in the sentence, such as ραμμένο, which is also in the neuter singular form.

στο is the contracted form of σε + το.

• σε = in, on, at, to
• το = the
• σε το becomes στο

So στο πουκάμισό μου literally means something like on/in/to the shirt of mine, but in natural English here it means on my shirt.

Greek σε is a very flexible preposition. Depending on context, it can mean:

• in
• on
• at
• sometimes to

In this sentence, since a button is attached to a shirt, English naturally uses on, so στο πουκάμισό μου is understood as on my shirt.

This is a stress rule involving enclitics, and μου is an enclitic.

The basic word is:

• πουκάμισο = shirt

When μου (my) follows it, Greek often adds an extra written accent to show the pronunciation clearly:

• πουκάμισο
• πουκάμισό μου

So the extra accent does not mean it is a different word; it shows the stress pattern when μου is attached after it.

In Greek, possessive words like μου (my), σου (your), του (his/its) usually come after the noun.

So:

• το πουκάμισό μου = my shirt
• literally: the shirt my

This is completely normal in Greek.

δεν is the normal word for not before a verb.

Here:

• είναι = is
• δεν είναι = is not

So:

• δεν είναι καλά ραμμένο = is not sewn well / is not well sewn

In Greek, δεν usually comes directly before the verb.

Because ραμμένο is a past participle used like an adjective.

• ράβω = I sew
• ραμμένος / ραμμένη / ραμμένο = sewn

So είναι ραμμένο literally means is sewn. This is a very natural way in Greek to describe the state of something.

In this sentence:

• καλά ραμμένο = well sewn
• δεν είναι καλά ραμμένο = it is not well sewn

Because ραμμένο agrees with κουμπί, and κουμπί is neuter singular.

Greek adjectives and participles change form to match the noun they describe:

• ραμμένος = masculine
• ραμμένη = feminine
• ραμμένο = neuter

Since το κουμπί is neuter, the correct form is ραμμένο.

Here καλά means well, not good.

• καλός / καλή / καλό = good (adjective)
• καλά = well / properly (adverb)

Since it describes how the button is sewn, Greek uses the adverb:

• καλά ραμμένο = well sewn
• more naturally in English: properly sewn

Yes. It means the button on my shirt.

The structure is:

• Το κουμπί = the button
• στο πουκάμισό μου = on my shirt

So Greek is simply using a noun followed by a prepositional phrase, just like English does in the button on my shirt.

ραμμένο is pronounced roughly ra-ME-no.

A few useful points:

• the stress is on -μέ-
• μμ is pronounced like a normal m sound, but the double spelling reflects the word’s formation
• ραμμένο does not sound like two fully separate m sounds in careful everyday speech; it is just a strong m

So the important thing for a learner is mainly the stress: ra-ME-no.