pet·a·hertz 
(pĕtə-hûrts′)
(pĕtə-hûrts′)n. Abbr. PHz
One quadrillion (1015) hertz.
- interpretative
- interpreted language
- interpreter
- interpretive
- interpretively
- interpupillary
- interracial
- interregional
- interregnal
- interregnum
- interrelate
- interrelatedness
- interrelationship
- interreligious
- interrobang
- interrog.
- interrogate
- interrogation
- interrogational
- interrogation point
- interrogative
- interrogatively
- interrogator
- interrogatorily
- interrogatory