The Irish Bouzouki
I have been practicing my bouzouki. Guitar is my first and the mandolin is my second instrument. When playing a string instrument I always compare the tuning to guitar or mandolin. The guitar is tuned in fourth intervals except for the second string, which is tuned a third interval from the third string. The mandolin is tuned in fifth intervals. The bouzouki is a combination of fifth and fourth intervals. The third course (set of 2 strings) is a fifth interval from the fourth course. The second course is a fifth interval from the third course. And, the first course is a fourth interval from the second course. Therefore, the bouzouki feels like a combination of guitar and mandolin. The first and second courses feel like a guitar while the third and fourth courses feel like a mandolin.
The bouzouki is also similar to dadgad tuning on guitar. The bouzouki is tuned gdad. Therefore, the one, two, and three courses on the bouzouki are identical to the fourth, fifth, and six strings on the guitar.
The one, two, and three courses of the bouzouki are identical to the three courses of the mountian dulcimer.
In conclusion, the bouzouki is similar to the guitar, mandolin, and mountian dulcimer. When learning any string instrument, compare them to the instrument that you know.