- Elesemantium by Beklemishev-Petrov I. (0 features)
- ideolat (ideographic latin) by storpidul (1 feature)
- Illicraic by V. Espinosa (126 features)
- Ithkuil III by John Quijada (137 features)
- New Ithkuil by John Quijada (143 features)
- Toki Pona by Sonja Lang (139 features)