Print versus handwriting
Printed Arabic is based on the Naskh hand. Daily handwriting is closer to Ruq'ah, and looks different in small but important ways.
Printed Arabic — the script of newspapers, novels, screens, and most modern Qurans — is modelled on the calligraphic hand called Naskh. Naskh is the formal, careful, balanced book hand. It keeps every letter in its full classical shape, every dot in its place, every diacritic where it ought to go. It is unambiguous and easy to read. It is also slow to write. Almost nobody writes it by hand.
What educated Arabs actually write — at the kitchen table, in a meeting, on a chalkboard, in a notebook — is closer to Ruq'ah. Ruq'ah is the everyday workhorse hand of the eastern Arab world (the Levant, Egypt, the Gulf, Iraq); the Maghreb has its own handwriting traditions descended from Maghrebi. Both are pragmatic. They simplify, they speed up, they let dots merge or get implied, they let letters run together. Reading other people's handwriting in Arabic is its own skill, the way reading other people's cursive English used to be.
What changes between print and hand
Several recurring simplifications. They are not random; once you have seen each pattern in a few different hands you can predict them.
Dots merge or get strokes. Any letter with two dots — taa ت, qaaf ق, yaa ي — gets the two dots replaced by a small horizontal dash. Three dots — thaa ث, shiin ش — become a small caret or chevron. Single dots usually survive but can shrink to a hard tick. The reader knows which letter is which from context and from the body shape.
Teeth flatten. The strings of teeth that mark medial siin س, shiin ش, and the medial forms of baa, taa, thaa, nuun, yaa often get reduced to a single low stroke or even a flat line in fast handwriting. The reader works out the count of teeth from word context, again.
The taa marbuuTa shrinks. The careful, two-dotted, haa-shaped ة of print frequently becomes a single quick mark in handwriting — sometimes a small loop with a dash, sometimes essentially indistinguishable from a quickly-written haa. The reader supplies the gender ending from grammar.
Letters run together. Within a connected segment, where print preserves clear inter-letter joins, handwriting often elides them — the body of one letter flows into the next without a clear break, and the proportions of the medial forms shift to whatever the writer's hand finds easy.
The kaaf changes shape. The print kaaf ك has a distinctive square top with a small hamza-like flourish inside. The handwritten initial and medial kaaf is typically a simple loop with no internal mark, and a learner used to print form has to learn to recognise it.
Diacritics vanish. Vocalisation marks were already absent from most print; in handwriting they are essentially never written, except where the writer is consciously disambiguating a word for a learner or a child.
The traps for learners
A handful of letter pairs that look quite different in print look much more similar in handwriting, and these are where most learners stumble.
Kaaf and laam. Both are tall vertical strokes when written quickly. In print, kaaf has its distinctive interior mark; in handwriting that is often gone. Distinguishing them depends on the slight curve at the top (kaaf bends more) and on word context.
ʿAyn and ghayn. The only difference in print is the dot above the ghayn. In handwriting, where the dot may be a small dash or a quick tick, the reader leans on context. Worse, the loop of medial ʿayn and ghayn looks different in handwriting from in print — flatter, and easier to confuse with medial mim.
The medial haa. The medial form of haa ـهـ in print is a clear figure-eight or small double-loop. In handwriting it can be drawn as a single loop with a flick, and is easy to confuse with medial miim.
The five dotted letters that share a body. The body shape that gives baa, taa, thaa, nuun, and yaa is identical; only the dots distinguish them. In print this is unambiguous. In hand, with dots reduced to flicks or implied, the reader is very dependent on context.
Where to start
A few practical pointers for someone learning to write Arabic by hand.
Learn the connecting strokes from the start. Do not learn the four positional forms in isolation; learn how to write a small word and feel the join. The joining habit is the single biggest motor difference between writing Arabic and writing English, and the best way to internalise it is to write small connected words from day one.
The right-to-left motion is real. If you are right-handed and have written English all your life, you have spent decades trained to pull the pen across the page from left to right. Arabic asks you to push in the opposite direction, and at first the strokes feel uncontrolled. This passes within a week or two of consistent practice. There is nothing wrong with your hand; it has not done this motion before.
Write the body first, then the dots. Across nearly all calligraphic traditions, the rule is to write a complete word's bodies before going back to add the dots. This is partly aesthetic — uninterrupted strokes are nicer — and partly practical: it lets you see the whole shape before you commit to which letter is which. As a beginner, copying this habit pays off.
Use lined paper. Arabic baselines are real and the connecting strokes assume one. Plain printer paper teaches your hand bad habits. Any standard ruled notebook is fine.
Do not start with calligraphy. Naskh, Thuluth, and the rest are proper calligraphic disciplines and require a teacher and a reed pen. Just write Ruq'ah-style with a normal pen, copying from any modern Arabic textbook, and you will reach functional handwriting much faster.