1in·side 
/ɪnˈsaɪd, ˈɪnˌsaɪd/ noun
plural in·sides /ɪnˈsaɪd, ˈɪnˌsaɪd/ noun 1 [count] : an inner side, edge, or surface of something — usually singular ▪ The door can only be locked from the inside. — often + of ▪ I had a sore on the inside of my mouth. 2 a the inside : an inner part of something (such as a building or machine)
▪ The inside of the church is quite beautiful. ▪ I've never seen the inside of a computer before. — often plural ▪ the insides of a computer
b [count] informal : the inner parts (such as the heart and stomach) of a person's body — usually plural ▪ I felt like my insides were tied up in knots.
▪ The inside of the church is quite beautiful. ▪ I've never seen the inside of a computer before. — often plural ▪ the insides of a computer
b [count] informal : the inner parts (such as the heart and stomach) of a person's body — usually plural ▪ I felt like my insides were tied up in knots.
on the inside 1 : on the inner side, edge, or surface of something
▪ The number 22 car tried to pass the leader on the inside (of the track). 2 baseball : on the side of home plate nearest the batter
▪ The next pitch was a fastball on the inside. 3 — used to describe how someone is feeling ▪ She may have seemed happy, but really she was sad on the inside. 4 : in a position within an organization or group
▪ The bank robbers must have had help from someone on the inside. [=someone working for the bank that was robbed] 5 : in prison
▪ He wondered what life was like on the inside.
▪ The number 22 car tried to pass the leader on the inside (of the track).
▪ The next pitch was a fastball on the inside.
▪ The bank robbers must have had help from someone on the inside. [=someone working for the bank that was robbed]
▪ He wondered what life was like on the inside.
