IPA: /ˌɪnɪkˈspɪərəns/
KK: /ɪnɪkˈspɪərəns/
The state of not having enough experience or knowledge in a particular area or activity.
Her inexperience in handling the project led to several mistakes.
Inexperience is formed from "in-" (meaning not) and "experience" (from Latin "experientia", meaning knowledge or skill gained through experience). The word describes a lack of knowledge or skill due to not having experience.
Think of 'not' ('in-') having 'knowledge or skill' ('experientia') — that's why inexperience means lacking experience.