The ㅇ in 임 is a placeholder. ㅁ is not silent. The final consonant is optional but the first consonant is required for a syllable. Here is a quote from http://en.wikipedia.org/wiki/Hangul#Morpho-syllabic_blocks Except for a few grammatical morphemes prior to the twentieth century, no letter may stand alone to represent elements of the Korean language. Instead, letters are grouped into syllabic or morphemic blocks of at least two and often three: (1) a consonant or a doubled consonant called the initial (초성, 初聲 choseong syllable onset), (2) a vowel or diphthong called the medial (중성, 中聲 jungseong syllable nucleus), and, optionally, (3) a consonant or consonant cluster at the end of the syllable, called the final (종성, 終聲 jongseong syllable coda). When a syllable has no actual initial consonant, the null initial ㅇ ieung is used as a placeholder. (In modern Hangul, placeholders are not used for the final position.) Thus, a block contains a minimum of two letters, an initial and a medial. Although the Hangul had historically been organized into syllables, in the modern orthography it is first organized into morphemes, and only secondarily into syllables within those morphemes, with the exception that single-consonant morphemes may not be written alone.