Iso and neo vs. sec and tert

[Shruti Patel 2G]

Could someone explain what situations would use iso and neo versus when to use sec and tert? I can't seem to understand the difference in terms of what the molecules look like (both iso and sec have three carbons and neo and tert have four carbons in the same configuration). Thanks!

[Nikhil Davuluri 2A]

In iso the split of the carbons occurs at the end of the substituent chain whereas in sec the split of carbons occurs at the beginning of the substituent chain.

neo has a cross of carbons at the end of the substituent chain, while in tert, the substituent chain is bonded directly to the carbon at the center of the cross. This makes tert begin with a T shape.

Hope this helps

[VictoriaRoderick_3A]

For sec- the center carbon should be attached to two other carbons as well.