I1, i1, or I-1 may refer to:
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Haplogroup I-M253
Haplogroup I-M253, also known as I1, is a Y chromosome haplogroup. The genetic markers confirmed as identifying I-M253 are the SNPs M253,M307.2/P203.2, M450/S109, P30, P40, L64, L75, L80, L81, L118, L121/S62, L123, L124/S64, L125/S65, L157.1, L1 ...
, a human Y-chromosome haplogroup occurring at greatest frequency in Scandinavia
* , a 1926 Imperial Japanese Navy submarine
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Motorola i1, a smartphone by Motorola
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LB&SCR I1 class, a 1906 British class of 4-4-2 steam tank locomotives
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Polikarpov I-1
The Polikarpov I-1 was the first indigenous Soviet monoplane fighter. It had to be redesigned after the crash of the first prototype, and was eventually ordered into production in small numbers, but it was never accepted for service with the Sov ...
, a 1923 Soviet monoplane fighter
* I1, a
rank-into-rank axiom in mathematical set theory
* I won, as it is pronounced similarly
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