There are a total of 25 9-letter words containing 'plex', and the number may vary in different dictionaries. You can specify the dictionary and order.

• cataplexy ₂₅
• complexed ₂₇
• complexer ₂₆
• complexes ₂₆
• complexly ₂₉
• diplexers ₂₁
• duplexers ₂₂
• duplexing ₂₅
• duplexity ₂₄
• metroplex ₂₃
• multiplex ₂₅
• perplexed ₂₄
• perplexes ₂₃
• plexiform ₂₆
• simplexes ₂₃
• triplexes ₂₀
• funplexes ₂₁
• perplexer ₂₀
• triplexed ₁₉
• apoplexed ₂₁
• apoplexes ₂₀
• complexus ₂₂
• decomplex ₂₃
• implexion ₂₀
• unperplex ₂₀

There are 25 9-letter words containing plex in the well-known word game dictionary, 19 in the Scrabble US (US/Canada/Thailand - TWL/NWL) dictionary, and 24 in the Scrabble UK (International - SOWPODS/CSW) dictionary, and 16 in the Words with Friends (WWF) dictionary.