Final answer:
The prefix 'intra-' means 'within', as in intramural or intravenous referring to something occurring within specific boundaries or veins.
Step-by-step explanation:
The prefix intra- means 'within'. This can be seen in words like intramural, which refers to something occurring within the walls of an institution, or intravenous, meaning within or by way of the veins. The prefix is used to form words that indicate something happening inside or within boundaries.