Modifiers matching perturbation:

• strong,
• related,
• environmental,
• excessive,
• external,
• additional,
• random,
• local,
• anthropogenic,
• therapeutic,
• major,
• mechanical,
• electric,
• uncertain,
• physiological,
• novel,
• acute,
• small,
• optical,
• mental,
• uniform,
• periodic,
• chemical,
• physical,
• dynamic,
• natural,
• anatomic,
• artificial,
• chronic,
• under,
• electrical,
• psychological,
• minor,
• dynamical,
• severe,

Simple categories matching periodic:

• item,
• evaluation,
• structure,
• system,
• rendezvous,
• signal,
• meeting,
• hazard,
• storm,
• activity,
• action,
• work,
• material,
• wave,
• waveform,
• layer,
• motion,
• communication,
• disturbance,
• curve,
• task,
• episode,
• catastrophe,
• payment,
• pattern,
• property,
• component,
• income,
• movement,
• lattice,
• data,
• sound,
• document,
• phenomenon,
• event,
• behavior,
• line,
• forum,
• charge,
• difficulty,
• medium,
• report,
• condition,
• benefit,
• bill,
• service,
• expenditure,
• information,
• shape,
• receipts,
• process,
• statement,
• works,
• solid,
• perturbation,
• object,
• occurrence,
• publication,
• insulator,
• disaster,
• function,
• gathering,
• return,
• review,
• disclosure,
• cycle,
• expense,
• change,
• feature,
• backup,
• substrate,