Finding '마시다' from '마셔요'

In the regular examples taught here, a stem ending in ㅣ combines with -어요 , and ㅣ and ㅓ contract to ㅕ in both ordinary pronunciation and spelling.

마시- + -어요 → 마시어요 → 마셔요

기다리- + -어요 → 기다리어요 → 기다려요

Not every form containing ㅕ comes from this contraction. Apply this reverse analysis only when the surrounding form and dictionary evidence support a ㅣ -final stem.

Start by restoring the likely stem-ending combination behind 마셔요 .

Step 1: Reverse the contraction: 마셔요 → 마시어요 .

Step 2: Identify and remove -어요 : 마시어요 → 마시- .

Step 3: Add -다 to form the likely dictionary headword: 마시- + -다 → 마시다 .

Confirm the restored form in a dictionary when the word is unfamiliar.

Apply the same reverse analysis to the regular form 기다려요 .

Step 1: Restore the uncontracted combination: 기다려요 → 기다리어요 .

Step 2: Identify and remove -어요 : 기다리어요 → 기다리- .

Step 3: Add -다 : 기다리- + -다 → 기다리다 .

The same relationship appears in examples such as 빌려요 → 빌리어요 → 빌리다 and 내려요 → 내리어요 → 내리다 .

The same stem can also be recovered from the contracted past form 마셨어요 .

Restore the uncontracted combination first: 마셨어요 → 마시었어요 .

Then identify and remove -었어요 : 마시었어요 → 마시- .

Finally, add -다 : 마시- + -다 → 마시다 .

Analyze the full word rather than treating 셨 as an independent unit.

A common mistake is replacing 요 directly with 다 . That produces incorrect forms such as 마셔다 and 기다려다 .