mm mammal 哺乳動物 [Card #2; 字卡第2張: 第3個單字]
mm = /m/（2個相同子音在一起, 只發一個音）

Some more examples（更多例字）：hammer, stammer, simmer, shimmer, summer, bummer, grammar, gamma, comma, dilemma, common, comment, commence, commerce, commercial, immerse, imminent, immune, immunize, immunization, immediate, communicate, accommodate, consummate, command, commend, recommend, commit, committee, commodity, community, commute, commotion, persimmon, summon, summit, plummet, grommet, gimmick, mamma, momma, mommy, mummy, dummy, gummy, tummy, yummy, symmetry, summary, scrimmage, rummage, hammock, mammoth, pummel