HSK 5
不然
bùrán连（形）
not so; no; or else; otherwise
快点走不然会错过火车。
Kuài diǎn zǒu bù rán huì cuò guò huǒ chē.
Hurry, or you will miss the train.
Say it
Hold the button, say it, then let go.
Other HSK words sharing a character
Also free:
Appears across levels (5（7-9）) in the HSK 3.0 word list.