liminal

Relating to a transitional or initial stage; occupying a position on both sides of a boundary or threshold.

• liminality/ˌlɪmɪˈnælɪti/(n)阈限性

• liminal space
• liminal state
• liminal experience
• liminal period

1. 1.Airports are liminal spaces — you're neither where you came from nor where you're going. (in-between)
2. 2.Adolescence is a liminal period between childhood and adulthood. (transitional)

• transitional/trænˈzɪʃənəl/— between stages
• intermediate/ˌɪntəˈmiːdiət/— in between
• threshold/ˈθrɛʃhəʊld/— at the boundary, noun

from Latin "limen" = threshold — at the threshold, the point of transition