speleological (also spelaeological)

adj: speleological exploration 洞穴探索.

speechify, speechless, speechlessly, speechlessness, speed, speed limit, speed merchant, speed trap, speed up, speed-boat, speed-indicator, speed-up, speedboat, speedily, speediness, speeding, speedometer, speedway, speedwell, speedy, speleologist (also spelaeologist), speleology (also spelaeology), spell, spellbinder, spellbinding, spellbound, speller, spelling, spelt, spelunker, spend, spend...time (in) doing, spender, spending, spendthrift, spent, sperm, sperm whale, spermaceti, spermatozoon,