便携式 biànxiéshì portable

怎么记住“便携式”: 便 convenient + 携 to carry + 式 style = portable.

汉字

An attributive meaning 'portable' for devices - 便携式电脑 (biànxiéshì diànnǎo) a portable/laptop computer; 便携式充电器 (portable charger).
The 式 (type/style) makes it a modifier; it always precedes a noun, you don't say something 很便携式.
Tech/product register. Colloquially people often just say 便携 (biànxié) as an adjective: 很便携 (very portable).