It's Monday's ordinary thing.
With its triangular flap and lickable seal, with its opposite upper corners for stamp and return address, the way it conceals, protects, carries our messages and secrets and greetings and cards.
Envelopes can be thin or thick, sometimes faintly crosshatched from within by the blue security lining. Invitations often contain envelopes-within-envelopes, like Russian dolls, and these may be lined with silver or gold foil. Envelopes are objects we hold, press, seal, and when someone is being aggressive or risky we call it pushing the envelope. My favorite as a kid were the birthday or Christmas envelopes that came in the mail with real money.
What do you remember, what might you observe, about the lowly envelope?