Corresponding to $\ce{C5H12O}$ there will be a total of 14 structural isomers.
8 isomers with alcohol functional group:
(1) $\ce{CH3CH2CH2CH2CH2OH}$ : n-pentanol
(2) $\ce{CH3CH2CH2CH(OH)CH3}$ : 2-pentanol
(3) $\ce{CH3CH2CH(OH)CH2CH3}$ : 3-pentanol
(4) $\ce{CH3CH2C(CH3)(OH)CH3}$ : 2-methyl-2-butanol
(5) $\ce{CH3CH2CH(CH3)CH2OH}$ : 2-methyl-1-butanol
(6) $\ce{CH3CH(OH)CH(CH3)CH3}$ : 3-methyl-2-butanol
(7) $\ce{CH3CH(CH3)CH2CH2OH}$ : 3-methyl-1-butanol
(8) $\ce{CH3C(CH3)2CH2OH}$ : 2,2-dimethyl-1-propanol
6 isomers with ether functional group:
(1) $\ce{CH3CH2CH2CH2-O-CH3}$ : methyl butyl ether
(2) $\ce{CH3CH2CH2-O-CH2CH3}$ : ethyl propyl ether
(3) $\ce{CH3CH(CH3)CH2-O-CH3}$ : methyl isobutyl ether
(4) $\ce{CH3CH2-O-CH(CH3)CH3}$ : ethyl isopropyl ether
(5) $\ce{CH3CH2CH(CH3)-O-CH3}$ :methyl sec-butyl ether
(6) $\ce{(CH3)3-C-O-CH3}$ : methyl tert-butyl ether