Semi-fungible assets have very unique properties and may shift between being fungible and non-fungible during their lifecycle. After a specific period of time, or after certain conditions are met, semi-fungible assets may switch their fungibility between fungible and non-fungible.
For example, an Amazon gift card has the same value as any other identical gift card with the same expiration date and starting value. However, after redeeming the gift card, or after the validity expires, it is no longer the same as other non-redeemed and unexpired gift cards. The card becomes non-fungible as it has lost its exchangeable value.
Another example is a concert ticket for a band’s live performance. The ticket’s face value at the beginning of circulation can change later depending on supply and demand. And the value of the ticket might be slightly different than seats right next to you. You may be able to exchange your concert ticket for an identical ticket as long as it belongs to the same band, has the same date, and gives you a spot in the same seating area. After the concert, you can no longer exchange the token for another concert ticket for a later date or any other band on the same day. But you can collect the expired ticket as a keepsake. Though that scrapbook item will have a different value, which may also change over time, than the original ticket for the live experience.
See also the terms for fungible and non-fungible.