IPA: /ˈlaɪflɛs/
KK: /ˈlaɪfˌlɛs/
Not having life; dead or inanimate. It can also mean lacking energy or excitement.
The flowers looked lifeless after being left in the sun for too long.
Lifeless → It is formed from "life" (from Old English "līf", meaning existence or living) and "-less" (meaning without). The word "lifeless" means without life or lacking vitality.
Think of 'life' as existence and remember that 'lifeless' means lacking that existence.