I –  Homonym of a 3 letter body part

NI – What Monty Python’s Knights said

EIN – German indefinite article

DINE – Have a meal

TINED – Like a fork or a rake

DETAIN – Keep in custody for questioning

FAINTED – Had a syncopal episode

INFLATED – Added helium to the balloon

DEFLATION – A decline in prices for goods and services

DEFOLIANTS – Chemicals like Agent Orange