choosing a conjunction and the relationship it expresses:
------you buy a rare manuscript, make certain of its authenticity.
I used "Before" but it would be "time"
or
Should I use "If" and it would be "condition"
This is so confusing!!!
I'd use "Before."
Choosing the appropriate conjunction and understanding the relationship it expresses can indeed be confusing. In the sentence you provided, "you buy a rare manuscript, make certain of its authenticity," you are looking for a conjunction that signifies either a temporal relationship or a conditional relationship.
If you want to convey a temporal relationship, indicating the order of events, you could use the conjunction "before." For example, "Before you buy a rare manuscript, make certain of its authenticity." In this case, "before" indicates that the action of making certain of the authenticity should occur prior to buying the manuscript.
If you want to convey a conditional relationship, indicating a prerequisite or condition for taking action, you could use the conjunction "if." For example, "If you buy a rare manuscript, make certain of its authenticity." Here, "if" suggests that buying the manuscript is the condition that allows for the action of making certain of its authenticity.
It's important to carefully consider the meaning and intention you want to convey in order to select the appropriate conjunction.