The difference between 想念 and 怀念
The verbs 想念 and 怀念 have the same meaning, but differ slightly in usage.
The verb 想念
The verb 想念 
emphasizes that a person misses someone.
想念 is most commonly used in spoken language.
emphasizes that a person misses someone.
想念 is most commonly used in spoken language. Pay attention
We can use the verb 想念 when talking about people who are still alive or things that still exist.
Examples
女儿告诉我，她很想念出差的爸爸
My daughter told me that she misses her dad when he goes on business trips
nǚ'ér gàosu wǒ, tā hěn xiǎngniàn chūchāi de bàba
再次感谢你们，我会想念你们的
I'd like to thank you again. I will miss you
zàicì gǎnxiè nǐmen, wǒ huì xiǎngniàn nǐmen de
旅行期间她想念家里的舒适
She misses the comforts of home while traveling
lǚxíng qíjiān tā xiǎngniàn jiā lǐ de shūshì
The verb 怀念
The verb 怀念 emphasizes that a person remembers someone or something.
emphasizes that a person remembers someone or something. Pay attention
We can use the verb 怀念 when talking about people who are no longer living or things that no longer exist.
Examples
她非常怀念年轻时在国外留学的那段生活
She misses the life she had when she studied abroad in her youth
tā fēicháng huáiniàn niánqīng shí zài guówài liúxué de nà duàn shēnghuó
我很爱我的爷爷，我也很怀念他
I loved my grandfather and I miss him very much
wǒ hěn ài wǒ de yéye, wǒ yě hěn huáiniàn tā
很多人都怀念过去的好时光
Many people miss the good old days
hěn duō rén dōu huáiniàn guòqù de hǎo shíguāng
We can use the verbs 怀念 and 想念 interchangeably in the meaning "to miss".
Examples
每次回忆起小时代的学生生活，我最怀念的人就是王老师
Every time I reminence about my life as a student, the person I miss the most is Mr.Wang
měi cì huíyì qǐ xiǎo shídài de xuésheng shēnghuó, wǒ zuì huáiniàn de rén jiù shì wáng lǎoshī
每次回忆起小时代的学生生活，我最想念的人就是王老师
Every time I reminence about my life as a student, the person I miss the most is Mr.Wang
měi cì huíyì qǐ xiǎo shídài de xuésheng shēnghuó, wǒ zuì xiǎngniàn de rén jiù shì wáng lǎoshī