Ardeiul este în jardinieră.

Because Romanian usually puts the definite article at the end of the noun, not before it.

• ardei = pepper
• ardeiul = the pepper

So -ul is the masculine singular definite article here.

This is one of the first big differences from English:

• English: the pepper
• Romanian: ardeiul

That is a very good question, because ardei can be confusing for learners.

The form ardei can be:

• singular indefinite in dictionary-style form: ardei = pepper
• plural indefinite in ordinary use: ardei = peppers

Context usually tells you which one is meant.

In your sentence, there is no ambiguity because you have ardeiul, which is clearly singular definite: the pepper.

For comparison:

• un ardei = a pepper
• ardeiul = the pepper
• ardei = peppers
• ardeii = the peppers

Este is the 3rd person singular present of a fi, meaning to be.

So:

• este = is

Yes, in everyday Romanian, e is very common and natural:

• Ardeiul este în jardinieră.
• Ardeiul e în jardinieră.

Both are correct.
Este sounds a bit more careful, neutral, or formal; e sounds more conversational.

Romanian often uses a bare noun after a preposition in common location expressions, especially when the sentence is simply telling you where something is.

So în jardinieră is a natural way to say that the pepper is located in a planter/window box.

If you say într-o jardinieră, you are more explicitly saying:

• in a planter
• one planter among possible others

So the difference is roughly:

• în jardinieră = a simple location phrase
• într-o jardinieră = in a planter, with clearer indefinite meaning

Romanian does this with many place expressions, so learners often notice that articles are not always used where English expects a or the.

Because Romanian does not always mark location nouns the same way English does.

The noun jardinieră is feminine:

• jardinieră = planter
• jardiniera = the planter

But after prepositions like în, Romanian often allows the noun without an article in a location expression:

• în casă = in the house / at home
• în grădină = in the garden
• în jardinieră = in the planter

If you want to point to a clearly identified, specific planter, Romanian can also use a more explicit form such as:

• în jardiniera aceea = in that planter

So the bare form is not wrong or incomplete; it is a normal Romanian pattern.

A rough pronunciation is zhar-di-ni-E-rə.

A few useful points:

• j in Romanian sounds like the s in measure
• ă is a short neutral vowel, like the final a in sofa
• the stress is on e: jar-di-ni-E-ră

So the last syllable is not a strong English ra sound. It is softer: rə.

În contains the Romanian vowel î, which does not have an exact English equivalent.

A simple learner approximation is something like a tight, central vowel said with relaxed lips. If that feels too technical, just remember:

• it is not the English ee
• it is not the English oo
• it is a central Romanian sound that you will hear very often

The word în means in, and it is very common.

Not exactly.

In Romanian, ardei usually refers to the vegetable or pepper plant:

• bell pepper
• sweet pepper
• hot pepper, depending on context

But the spice black pepper is usually piper, not ardei.

So in this sentence, ardeiul is understood as the pepper plant or pepper vegetable in the planter, not the spice.

The order in your sentence is the most neutral one:

• Ardeiul = subject
• este = verb
• în jardinieră = location

So Ardeiul este în jardinieră is a straightforward, neutral sentence.

Romanian word order is fairly flexible, though. You could also hear:

• În jardinieră este ardeiul.

That version puts more emphasis on the location, as if answering Where is the pepper?

So the original sentence is the best basic pattern to learn first.

• ardei is masculine
• jardinieră is feminine

Gender matters because it affects:

• the definite article
• adjective endings
• sometimes pronouns and agreement

For example:

• ardeiul roșu = the red pepper
• jardiniera mare = the big planter

So learning the noun together with its gender will help you build correct Romanian sentences more easily.