Both を通じて and を通して mean 'through' or 'via', but they have a slight nuance. を通じて often emphasizes the entire process or period, while を通して can also mean 'throughout' a duration. For example, を通じて can be used for 'throughout one's life' (一生を通じて) and also for 'through a friend' (友達を通じて). を通して is more common in everyday speech for 'via a person or tool', like 'through the internet' (インターネットを通して). When the noun is a person, both work, but を通じて sounds a bit more formal. When the noun is a period of time, を通じて often means 'throughout', while を通して also means 'throughout', but を通して can also mean 'by means of' with a period? Actually, for time, を通じて is more typical for 'throughout', but を通して is also possible. In practice, they are interchangeable in many contexts, but を通じて is slightly more formal and written, while を通して is more neutral and used in both speaking and writing. For N3, you can use them interchangeably for 'through a person or means', but for 'throughout a period', を通じて is more common in textbooks. However, a learner can use を通して for both without sounding unnatural in casual conversation. The verb 通じる also means 'to be connected' and 通す means 'to let through', but this pattern is fixed with the noun preceding. Note: The noun must be a means or a medium, not an action. For actions, you use ことによって or によって. Example: 話し合いを通じて (through discussion) is fine because 話し合い is a noun. So it's noun + を通じて, not verb + を通じて.