Pignus parvum est, sed ludus iucundus est.

Both are nominative singular, because each one is the subject of its own clause:

• Pignus parvum est = the stake is small
• sed ludus iucundus est = but the game is pleasant/fun

With est, the subject is nominative, and a predicate adjective describing it is nominative too.

Because parvus, parva, parvum must agree with the noun it describes. Here it describes pignus, which is neuter singular, so the adjective must also be neuter singular:

• masculine: parvus
• feminine: parva
• neuter: parvum

So pignus parvum means a small stake.

Because iucundus agrees with ludus, and ludus is masculine singular. So the adjective must also be masculine singular nominative:

• ludus iucundus = a pleasant/fun game

If the noun were neuter, then you would expect iucundum instead.

Because not all neuter nouns belong to the second declension. Pignus is a third-declension neuter noun, so its nominative singular form is pignus, not pignum.

That is an important lesson for Latin learners: grammatical gender is not always obvious from the English meaning, and neuter nouns do not all look alike.

Yes, Latin can sometimes omit a repeated est when it is easily understood. So a shorter version like Pignus parvum est, sed ludus iucundus could work in context.

But repeating est is completely normal and often clearer, especially for learners. Here the sentence is simply made of two full clauses joined by sed:

• Pignus parvum est
• sed ludus iucundus est

Because ludum is accusative singular, and that case is usually used for a direct object. Here ludus is not an object; it is the subject of est. So it must be ludus, nominative singular.

The adjective also matches that nominative form:

• correct: ludus iucundus est
• not here: ludum iucundum est

Yes. Latin word order is more flexible than English because the endings show the grammatical relationships. You could rearrange the words for emphasis, for example:

• Parvum pignus est, sed ludus iucundus est
• Pignus parvum est, sed iucundus ludus est

The exact emphasis may shift a little, but the core meaning stays the same. The original order is straightforward and natural.

Sed means but. It links the two clauses and shows contrast:

• the stake is small
• but the game is pleasant/fun

So sed signals that the second idea contrasts with the first one.