Traditionally, Linguists stated that there are two different LEs in Chinese in terms of the positions in sentences. Le1 is used after the verbs and Le2 is used as the sentence particle. For examples,
tā shēng-le1 bìng le2
3p.sg catch-LE sickness LE
‘She is sick.’
However, Chu (2016) and Liu (2017) stated that there was only one LE in Chinese. Chu (2016: 169) observed that in the presence of le2, le1 can be freely omitted.
nà-běn shū kàn-wán-le1 hǎo-jǐ-tiān le2
nà-běn shū kàn-wán-( ) hǎo-jǐ-tiān le2
“That book had been read through many days.”