zehntausend
ten thousand
The cardinal number 10,000, which is the product of ten and one thousand.
Bei dem Marathon liefen über zehntausend Menschen mit.
Over ten thousand people took part in the marathon.

ten thousand
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ten thousand
The cardinal number 10,000, which is the product of ten and one thousand.
Bei dem Marathon liefen über zehntausend Menschen mit.
Over ten thousand people took part in the marathon.

The number 'zehntausend' (ten thousand) is made up of 'zehn' (ten) and 'tausend' (thousand). In German, cardinal numbers under one million are written as a single word.
Das Stadion fasst zehntausend Zuschauer.
The stadium holds ten thousand spectators.
When you want to express an approximate, large quantity, you can use the nominalized form 'Zehntausende' (tens of thousands). It is capitalized and often appears with 'von' (of) and the dative plural.
Zehntausende von Vögeln rasten hier jedes Jahr.
Tens of thousands of birds rest here every year.
When 'zehntausend' (ten thousand) stands directly before a noun, it is usually not declined. It keeps its base form, no matter which case the noun is in.
Die Reparatur des Autos kostet zehntausend Euro.
The car repair costs ten thousand euros.
thousand
'tausend' and 'zehntausend' are numbers and can easily be confused because both contain the word 'tausend'. But the difference is large: 'tausend' means 1,000, while 'zehntausend' means 10,000. So 'zehntausend' is ten times as much. In addition, 'tausend' can also colloquially mean simply 'very many', for example in 'tausend Dinge' (a thousand things). 'zehntausend' is normally used as an exact number. Pay special attention to 'zehn' at the beginning: it changes the quantity a lot.

Die Eltern haben für die Renovierung zehntausend Euro gespart.
The parents have saved ten thousand euros for the renovation.
Für das alte Fahrrad möchte der Verkäufer tausend Euro haben.
The seller wants a thousand euros for the old bicycle.