May luha dahil masakit ang mata.

May is an existential word. In this sentence, it means there is / there are.

So May luha literally means There are tears.

A very common other use of may is possession:

• May pera siya. = He/She has money.

So depending on context, may can mean there is/are or has/have.

Because may typically introduces the existence of something, and the noun after it usually does not take ang.

So:

• May luha. = There are tears.

Not:

• May ang luha. ✗

This is just how the pattern works in Filipino: may + noun.

It can be understood as tears in a general sense. Filipino nouns often do not have to show singular vs. plural unless you want to make it explicit.

• luha = tear / tears
• mga luha = tears, explicitly plural

In natural speech, May luha is fine even if English would use the plural tears.

Filipino often puts the predicate first. That means the describing word or idea comes before the ang-marked topic.

So:

• Masakit ang mata.
  Literally: Painful the eye.
  Natural meaning: The eye hurts.

This predicate-first pattern is very common:

• Maganda ang bahay. = The house is beautiful.
• Mainit ang sabaw. = The soup is hot.

Here, ang marks the topic or focus of the sentence.

In Masakit ang mata, the thing being described as painful is ang mata.

So the structure is roughly:

• masakit = painful / hurts
• ang mata = the eye, as the topic of the statement

You should not think of ang as always exactly equal to English the. Sometimes it overlaps with the, but its grammar role in Filipino is different.

These are two different structures.

• Masakit ang mata. = The eye hurts.
  This is a full sentence.

• masakit na mata = a painful/sore eye
  This is a noun phrase, not a full sentence.

The -ng / na linker is used when one word directly modifies another inside a phrase. But in Masakit ang mata, masakit is the predicate of the sentence, so no linker is used.

By itself, mata is normally eye in the singular.

• mata = eye
• mga mata = eyes

So masakit ang mata most directly means the eye hurts. In real-life context, people may sometimes say the singular even when speaking generally about eye pain, but grammatically it is singular here.

Dahil means because.

So:

• May luha dahil masakit ang mata. = There are tears because the eye hurts.

It is similar to kasi, which also means because, but kasi is usually more conversational.

Compare:

• May luha dahil masakit ang mata. = neutral / standard
• May luha kasi masakit ang mata. = more casual

Both are common, but dahil can sound a bit more formal or written.

In this sentence, luha is a noun meaning tear or tears.

But there is also a related verb:

• lumuha = to shed tears
• lumuluha = crying / shedding tears / teary

So a related sentence could be:

• Lumuluha dahil masakit ang mata. = [Someone] is tearing up because the eye hurts.

That is different from May luha, which simply states that tears are present.

It is understandable and grammatically fine, but in everyday speech, some speakers might prefer a more verbal expression, depending on what they want to emphasize.

For example:

• Lumuluha dahil masakit ang mata. = [Someone] is tearing up because the eye hurts.
• May luha kasi masakit ang mata. = There are tears because the eye hurts.

Your sentence is natural enough, especially if the focus is on the presence of tears.

Yes. You can reverse them, and the meaning stays very similar, though the emphasis changes.

• May luha dahil masakit ang mata.
• Masakit ang mata kaya may luha.

The first starts with the result: there are tears.
The second starts with the cause: the eye hurts.

Both are possible; the speaker just chooses what to highlight first.