"alternating" - key terms from Wikipedia

alternating
alternating	bass
alternating	current
alternating	current generator
alternating	current motor
alternating	currents
alternating	feet
alternating	form
alternating	harmonic series
alternating	permutations
alternating	role
alternating	rounds
alternating	series
alternating	single and double bonds
alternating	sounds
alternating	sum
alternating	tread stairs
leaves alternating
phase alternating	line
regularly alternating