Pauk je bio ispod klupe, ali ga je moj unuk ipak vidio.

In Croatian, je is the auxiliary verb to be in the 3rd person singular present. It is used to form the past tense together with the past participle:

• bio = been / was
• je bio = was

So:

• Pauk je bio ispod klupe = The spider was under the bench

Unlike some languages, standard Croatian normally requires the auxiliary here.

Ispod means under / below, and it normally takes the genitive case when it expresses location.

So:

• klupa = bench
• klupe = of the bench / under the bench (genitive singular here)

That is why Croatian says:

• ispod klupe = under the bench

This is a very common pattern:

• ispod stola = under the table
• ispod kreveta = under the bed

Ga is the accusative singular masculine animate clitic pronoun, meaning him/it.

Here it refers back to pauk (spider), which is a masculine noun in Croatian. Since the spider is the direct object of vidio (saw), Croatian uses the accusative pronoun:

• ga je moj unuk vidio = my grandson saw it

Even though English uses it for animals in many contexts, Croatian grammar still follows the noun’s grammatical gender, so pauk becomes ga.

Both are possible, but Croatian often places short unstressed words called clitics near the beginning of the clause, usually in the second position.

In this sentence:

• ali ga je moj unuk ipak vidio

the clitics are:

• ga = him/it
• je = auxiliary has/was

They come early in the clause, after ali.

So this word order is very natural in Croatian.
You could also hear:

• ali moj unuk ga je ipak vidio

but the given version is especially typical because of clitic placement.

They are doing two different jobs:

1. Pauk je bio...

   • je bio forms the past tense of biti (to be)
   • meaning: was

2. ga je moj unuk ipak vidio

   • je vidio forms the past tense of vidjeti (to see)
   • meaning: saw

So both are auxiliary uses of je, but with different past participles:

• bio = been / was
• vidio = seen / saw

Ipak means something like:

• still
• nevertheless
• all the same
• even so

In this sentence it suggests a contrast: the spider was hidden under the bench, but the grandson saw it anyway.

So ipak adds the idea of surprise or contrast:

• ali ga je moj unuk ipak vidio = but my grandson saw it anyway / nevertheless

In standard Croatian, the masculine singular past participle of vidjeti is usually vidio.

So:

• vidio = saw

Learners may notice forms like video in some Serbian usage, but in standard Croatian vidio is the expected form.

Similarly:

• radio = worked
• nosio = carried
• gledao = watched

Moj unuk is the subject of the second clause, so it is in the nominative case:

• moj = my
• unuk = grandson

Since he is the one doing the action (seeing), nominative is required.

Compare:

• moj unuk = my grandson (subject)
• moga unuka = my grandson in a different case, for example as an object in some contexts

Here:

• moj unuk je vidio... = my grandson saw...

Yes, pauk is masculine.

One clue is that many Croatian masculine nouns in the nominative singular end in a consonant:

• pauk = spider
• grad = city
• stol = table

You can also see masculine agreement elsewhere in the sentence:

• bio is masculine singular
• ga refers to a masculine noun

If the noun were feminine, those forms would be different.

Past participles in Croatian agree with the subject in gender and number.

The subject is pauk, which is masculine singular, so the participle must also be masculine singular:

• masculine singular: bio
• feminine singular: bila
• neuter singular: bilo

So:

• Pauk je bio... = masculine
• If it were mačka (cat, feminine), it would be Mačka je bila...

Yes. Croatian word order is more flexible than English word order, although some versions sound more natural than others.

Possible alternatives include:

• Pauk je bio ispod klupe, ali moj ga je unuk ipak vidio.
• Pauk je bio ispod klupe, ali moj unuk ga je ipak vidio.

The original:

• Pauk je bio ispod klupe, ali ga je moj unuk ipak vidio.

sounds very natural because the clitics ga je are placed early in the clause.
The meaning stays basically the same, but emphasis can shift slightly depending on word order.

Vidio comes from vidjeti, which is generally treated as an imperfective verb in Croatian, although in practice see often behaves like a completed event in translation.

Here the sentence simply reports a past event:

• moj unuk ga je vidio = my grandson saw it

Croatian does not always match English tense-aspect distinctions exactly. In this context, vidjeti is the normal verb to use for to see.

If the idea were more like caught sight of or noticed, Croatian might also use verbs such as ugledati or primijetiti, depending on nuance.

Because ali means but, and it introduces a new clause. In Croatian, as in English, a coordinating conjunction like ali commonly separates two clauses, so a comma is used:

• Pauk je bio ispod klupe, ali ga je moj unuk ipak vidio.

This helps mark the contrast between the two parts:

1. the spider was under the bench
2. the grandson still saw it