When you are face-to-face with a friend, what’s the “mode” of your interaction?
What’s the mode of your interaction if you’re talking to your friend on the phone?
What’s the mode of your interaction if you’re writing your friend a letter or reading one they’ve written?
The “mode” is the manner in which something is experienced. The Eucharist is Jesus’ body, blood, soul and divinity in sacramental mode. That is, He is present sacramentally, not physically.