Pullback (limit of a cospan A→C←B) and pushout (colimit of a span A←C→B); specialise to fibre products, amalgamated free products, fibre bundles, and mapping cylinders.
Pullback (limit of a cospan A→C←B) and pushout (colimit of a span A←C→B); specialise to fibre products, amalgamated free products, fibre bundles, and mapping cylinders.