1. straw [noun] [het rietje, de rietjes] [‘riet-ju’]

When referring to the object with which to suck up fluids, the Dutch have chosen to use the diminutive of a plant with a similar shape: "riet": the long, hard grass that grows in shallow, calm waters.

As a translation, "reed" can be used too, but in the context of the wood-wind instruments, see 2.

Examples:
– "Mam, ik wil een rietje!"
("Mum, I want a straw!")

– "Als je bier met een rietje drinkt, word je sneller zat."
("If you drink beer with a straw, you get drunk faster." Note that "word" does not get the additional ‘t’ since the second person "je" and the verb are swapped.)

– "Mag ik twee bier en een cola alsjeblieft." – "Natuurlijk, wil je een rietje bij de cola?"
("Can I have two beers and a coke please." – "Sure, do you want a straw with the coke?")

Related word:
– "Parapluutje": little umbrella.

2. reed [noun] [het rietje, de rietjes] [‘riet-ju’] 

Most of the wood-wind instruments have a small, flat piece of wood, which is part of the mouthpiece, and which produces the actual sound by vibration when blowing the instrument: the reed.

Examples:
– "Mijn klarinet is vals." – "Misschien moet je het rietje vervangen."
("My clarinet is out of tune." – "Perhaps you should replace the reed.")

Related word:
– "Houten blaasinstrument": wood-wind instrument.