elongation

US /ɪˌlɑːŋˈɡeɪ.ʃən/
UK /ɪˌlɑːŋˈɡeɪ.ʃən/
1.

sự kéo dài

the process of becoming or making something become longer, and often thinner:

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Yoga postures emphasize elongation of the spine and help condition the back.