• I -ARE -ATUM PORTARE PORTATUM
• II -ERE -TUM DOCERE DOCTUM
• III -ERE -TUM DUCERE DUCTUM
• IIIio -ERE -TUM CAPERE CAPTUM
• IV -IRE - (I)TUM AUDIRE AUDITUM

• VENIRE VENTUM

Verbs ending in a dental (d, t) usually have -SUM instead of -TUM

• SENTIRE SENSUM
• MITTERE MISSUM
• VIDERE VISUM
• CADERE   CASUM
• CAEDERE CAESUM

Sometimes there is assimilation for ease in pronunciation: b > p; g > c

• LEGERE LECTUM
• AGERE ACTUM
• SCRIBERE SCRIPTUM

Some Verbs are irregular, for example:

• PELLERE PULSUM
• MANERE MANSUM