Hmmm

Part of speech: interjection

Definitions

1. An wordless vocal sound made to show that someone is thinking, doubtful or undecided about something
2. A murmured noise of consideration or uncertainty that a speaker produces while weighing an idea
3. Interjection voiced to signal pondering, skepticism or reluctance before giving an answer or opinion

Etymology: "Hmmm" is an elongated form of "hmm", the wordless sound of thinking, doubt or mild inquiry. Its root is the verb "hum", which is also the source of the sound's name. The stretched spelling simply lengthens the vowel-less murmur, so "hmmm" signals a longer, more drawn-out pause of consideration than the short "hmm" does.