Top panel: iron distribution of the three sub-populations of Terzan 5 (gray histogram and colored lines) compared to that of the Galactic bulge field stars from the literature (Ness et al. 2013; Johnson et al. 2014). Bottom panel: [α/Fe]-[Fe/H] distribution of the three sub-populations of Terzan 5 (extreme metal-poor: black circle; sub-solar: blue triangle; super-solar: red square) compared to that of the bulge field stars from the literature (gray dots). The formation epoch of the two major Terzan 5 sub-populations is also labeled.