Each meter, then, is some combination of four such units, which may be realized as spondees, dactyls, anapests, or as four light syllables.
If the import of the first line doesn't alert the reader to its metrical self-referentiality and poetic importance, the spondee closing the second almost certainly will.
These equivalences allow for easy substitutions of one foot by another e.g. a spondee can be substituted for a dactyl.
This term suggests a line of six dactyls, but a spondee can be substituted in most positions.
The sixth foot is either a spondee or a trochee.
The spondee typically does not provide the basis for a metrical line.
The other feet can be varied with a spondee, dactyl, tribrach, or more rarely an anapaest.
There is generally one accent in each foot of a line, unless the foot is a spondee (//).
