A string (or 1-brane) is a one-dimensional (1d) curvilinear path integral (integrand) with (at most) two (2) endpoints (in/input and out/output) called nuts. Strings may be open🔓 or closed🔒, but not both. (see also brane, SMALL brane, loopstring, string ludology, thread, walk)
Computationally, a string is a stream (sequence) of preimages (ie. a concatenation of flageolet pencils).
