perpend：细思，考虑，斟酌   

词根词缀：per-完全 + -pend-称量→仔细称量/掂量

• unstable
• unstinting
• unsuitable
• unsympathetic
• until
• unto
• untold
• untouchable
• unveil
• unwilling
• unwind
• unwonted
• unworldly
• up
• upbeat
• upbraid
• upchuck
• upcoming
• update
• upend
• upfront
• upgrade
• upheaval
• uphold
• upholster