This is the 10613th most frequent Russian word.
водородный
"Водородный" means "hydrogen" or "related to hydrogen."
The word 'водородный' (hydrogen) is used as an adjective to describe the type of engine, indicating that it operates using hydrogen as fuel.
Водородный двигатель является экологически чистым источником энергии.
A hydrogen engine is an environmentally friendly energy source.
Here, 'водородный' modifies 'цикл' (cycle) to specify a cycle involving hydrogen.
Учёные изучают водородный цикл в атмосфере.
Scientists are studying the hydrogen cycle in the atmosphere.
In this sentence, 'водородный' is used to describe 'батарею' (battery), indicating that the battery is associated with hydrogen technology.