火焰 (huǒyàn) is a noun meaning "flame" or "blaze." It refers to the visible, burning part of a fire. It can be used both literally to describe actual fire and figuratively to describe passion or intensity.
蜡烛的火焰在风中摇晃。
là zhú de huǒ yàn zài fēng zhōng yáo huàng.
The candle flame flickered in the wind.
他眼中燃烧着热情的火焰。
tā yǎn zhōng ránshāo zhe rèqíng de huǒyàn.
The flames of passion burned in his eyes.
壁炉里的火焰让整个房间暖和起来了。
bìlú lǐ de huǒyàn ràng zhěnggè fángjiān nuǎnhuo qǐlái le.
The flames in the fireplace warmed up the entire room.