Markerul este lângă banda adezivă.

Because -ul is the definite article attached to a masculine/neuter noun in Romanian.

• marker = a marker / marker
• markerul = the marker

Romanian usually puts the at the end of the noun instead of using a separate word like English does.

So:

• markerul este... = the marker is...

The basic noun is bandă = tape / strip / band.

When it becomes definite (the tape), it changes to banda.

So:

• bandă = a tape
• banda = the tape

This is a very common Romanian pattern with feminine nouns ending in -ă.

In Romanian, when a noun has a following adjective, the definite article usually goes on the noun, not on the adjective.

So:

• bandă adezivă = adhesive tape
• banda adezivă = the adhesive tape

The noun banda carries the definiteness, and the adjective adezivă simply agrees with it in gender and number.

This is different from English, where the comes before the whole noun phrase.

Because the adjective has to agree with bandă/banda, which is feminine singular.

• masculine singular: adeziv
• feminine singular: adezivă

Since banda is feminine singular, the adjective also has to be feminine singular:

• banda adezivă

Lângă means next to, beside, or near.

In this sentence:

• Markerul este lângă banda adezivă.
• The marker is next to / beside the adhesive tape.

It is a very common preposition for physical location.

In standard Romanian, yes, you normally need este here because it means is.

• Markerul este lângă banda adezivă. = The marker is next to the adhesive tape.

Romanian can often drop subject pronouns like el or ea, but it does not normally drop the verb to be in a full standard sentence like this.

Yes. Romanian word order is fairly flexible.

The neutral, most straightforward order is:

• Markerul este lângă banda adezivă.

But you could also say:

• Lângă banda adezivă este markerul.

That sounds more like Next to the adhesive tape is the marker, with extra focus on the location.

So the original sentence is the most natural basic version.

Because Romanian usually uses an enclitic definite article, meaning the article is attached to the end of the noun.

Compare:

• English: the marker

• Romanian: markerul

• English: the tape
• Romanian: banda

This is one of the big structural differences between English and Romanian.

The indefinite version would be:

• Un marker este lângă o bandă adezivă.

That means:

• A marker is next to an adhesive tape.

Compare:

• markerul = the marker

• un marker = a marker

• banda adezivă = the adhesive tape
• o bandă adezivă = an adhesive tape

Yes, marker is used in Romanian as a loanword, especially for a felt-tip marker or permanent marker.

Like many borrowed nouns, it still follows Romanian grammar:

• un marker
• markerul
• doi markeri

So even though it looks English, it behaves like a Romanian noun in the sentence.

A few sounds here are especially important for English speakers:

• ă is a short neutral vowel, like the a in sofa
• â is a central vowel with no exact English equivalent; it is deeper and more central than ă

Approximate help:

• lângă ≈ LUN-guh, but with the first vowel not exactly like English u
• adezivă ≈ ah-deh-ZEE-vuh

Also note:

• stress in markerul is usually MAR-ke-rul
• stress in adezivă is on zi: a-de-ZI-vă

Normally, the noun after lângă is in the form Romanian traditionally calls the accusative, but for regular nouns this often looks the same as the nominative.

So in practice, a beginner mostly just learns:

• lângă banda adezivă = next to the adhesive tape

You usually won’t see a big visible change in the noun itself here, especially with common nouns like this.

Sometimes, but the meaning shifts a little.

• lângă = right next to / beside
• aproape de = near / close to

So:

• Markerul este lângă banda adezivă. = the marker is right beside it
• Markerul este aproape de banda adezivă. = the marker is near it, but not necessarily directly next to it

So lângă is the better match for beside/next to.